LoongArch: Disable explicit reloc for TLS LD/GD with -mexplicit-relocs=auto

LoongArch: Disable explicit reloc for TLS LD/GD with -mexplicit-relocs=auto

Binutils 2.42 supports TLS LD/GD relaxation which requires the assembler
macro.

gcc/ChangeLog:

	* config/loongarch/loongarch.cc (loongarch_explicit_relocs_p):
	If la_opt_explicit_relocs is EXPLICIT_RELOCS_AUTO, return false
	for SYMBOL_TLS_LDM and SYMBOL_TLS_GD.
	(loongarch_call_tls_get_addr): Do not split symbols of
	SYMBOL_TLS_LDM or SYMBOL_TLS_GD if la_opt_explicit_relocs is
	EXPLICIT_RELOCS_AUTO.

gcc/testsuite/ChangeLog:

	* gcc.target/loongarch/explicit-relocs-auto-tls-ld-gd.c: Check
	for la.tls.ld and la.tls.gd.