LoongArch: Use standard pattern name and RTX code for LSX/LASX rotate shift

LoongArch: Use standard pattern name and RTX code for LSX/LASX rotate shift

Remove unnecessary UNSPECs and make the [x]vrotr[i] instructions useful
with GNU vectors and auto vectorization.

gcc/ChangeLog:

	* config/loongarch/lsx.md (bitimm): Move to ...
	(UNSPEC_LSX_VROTR): Remove.
	(lsx_vrotr_<lsxfmt>): Remove.
	(lsx_vrotri_<lsxfmt>): Remove.
	* config/loongarch/lasx.md (UNSPEC_LASX_XVROTR): Remove.
	(lsx_vrotr_<lsxfmt>): Remove.
	(lsx_vrotri_<lsxfmt>): Remove.
	* config/loongarch/simd.md (bitimm): ... here.  Expand it to
	cover LASX modes.
	(vrotr<mode>3): New define_insn.
	(vrotri<mode>3): New define_insn.
	* config/loongarch/loongarch-builtins.cc:
	(CODE_FOR_lsx_vrotr_b): Use standard pattern name.
	(CODE_FOR_lsx_vrotr_h): Likewise.
	(CODE_FOR_lsx_vrotr_w): Likewise.
	(CODE_FOR_lsx_vrotr_d): Likewise.
	(CODE_FOR_lasx_xvrotr_b): Likewise.
	(CODE_FOR_lasx_xvrotr_h): Likewise.
	(CODE_FOR_lasx_xvrotr_w): Likewise.
	(CODE_FOR_lasx_xvrotr_d): Likewise.
	(CODE_FOR_lsx_vrotri_b): Define to standard pattern name.
	(CODE_FOR_lsx_vrotri_h): Likewise.
	(CODE_FOR_lsx_vrotri_w): Likewise.
	(CODE_FOR_lsx_vrotri_d): Likewise.
	(CODE_FOR_lasx_xvrotri_b): Likewise.
	(CODE_FOR_lasx_xvrotri_h): Likewise.
	(CODE_FOR_lasx_xvrotri_w): Likewise.
	(CODE_FOR_lasx_xvrotri_d): Likewise.

gcc/testsuite/ChangeLog:

	* gcc.target/loongarch/vect-rotr.c: New test.