LoongArch: testsuite:Added support for vector object detection.

LoongArch: testsuite:Added support for vector object detection.

- Change the default vectorization "-mlasx" option to "-mlsx" because there
are many non-aligned memory accesses when using 256-bit vectorization.

- The following detection procedure is added to the target-supports.exp file:

1.check_effective_target_scalar_all_fma
2.check_effective_target_vect_int
3.check_effective_target_vect_intfloat_cvt
4.check_effective_target_vect_doubleint_cvt
5.check_effective_target_vect_intdouble_cvt
6.check_effective_target_vect_uintfloat_cvt
7.check_effective_target_vect_floatint_cvt
8.check_effective_target_vect_floatuint_cvt
9.check_effective_target_vect_shift
10.check_effective_target_vect_var_shift
11.check_effective_target_whole_vector_shift
12.check_effective_target_vect_bswap
13.check_effective_target_vect_bool_cmp
14.check_effective_target_vect_char_add
15.check_effective_target_vect_shift_char
16.check_effective_target_vect_long
17.check_effective_target_vect_float
18.check_effective_target_vect_double
19.check_effective_target_vect_long_long
20.check_effective_target_vect_perm
21.check_effective_target_vect_perm_byte
22.check_effective_target_vect_perm_short
23.check_effective_target_vect_widen_sum_hi_to_si
24.check_effective_target_vect_widen_sum_qi_to_hi
25.check_effective_target_vect_widen_sum_qi_to_hi
26.check_effective_target_vect_widen_mult_qi_to_hi
27.check_effective_target_vect_widen_mult_hi_to_si
28.check_effective_target_vect_widen_mult_qi_to_hi_pattern
29.check_effective_target_vect_widen_mult_hi_to_si_pattern
30.check_effective_target_vect_widen_mult_si_to_di_pattern
31.check_effective_target_vect_sdot_qi
32.check_effective_target_vect_udot_qi
33.check_effective_target_vect_sdot_hi
34.check_effective_target_vect_udot_hi
35.check_effective_target_vect_usad_char
36.check_effective_target_vect_avg_qi
37.check_effective_target_vect_pack_trunc
38.check_effective_target_vect_unpack
39.check_effective_target_vect_hw_misalign
40.check_effective_target_vect_gather_load_ifn
40.check_effective_target_vect_condition
42.check_effective_target_vect_cond_mixed
43.check_effective_target_vect_char_mult
44.check_effective_target_vect_short_mult
45.check_effective_target_vect_int_mult
46.check_effective_target_vect_long_mult
47.check_effective_target_vect_int_mod
48.check_effective_target_vect_extract_even_odd
49.check_effective_target_vect_interleave
50.check_effective_target_vect_call_copysignf
51.check_effective_target_vect_call_sqrtf
52.check_effective_target_vect_call_lrint
53.check_effective_target_vect_call_btrunc
54.check_effective_target_vect_call_btruncf
55.check_effective_target_vect_call_ceil
56.check_effective_target_vect_call_ceilf
57.check_effective_target_vect_call_floor
58.check_effective_target_vect_call_floorf
59.check_effective_target_vect_call_lceil
60.check_effective_target_vect_call_lfloor
61.check_effective_target_vect_logical_reduc
62.check_effective_target_section_anchors
63.check_vect_support_and_set_flags
64.check_effective_target_vect_max_reduc
65.check_effective_target_loongarch_sx
66.check_effective_target_loongarch_sx_hw

gcc/testsuite/ChangeLog:

	* lib/target-supports.exp: Add LoongArch to the list of supported
	targets.