Build: Set gcc_cv_as_mips_explicit_relocs if gcc_cv_as_mips_explicit_relocs_pcrel

Build: Set gcc_cv_as_mips_explicit_relocs if gcc_cv_as_mips_explicit_relocs_pcrel

We check gcc_cv_as_mips_explicit_relocs if gcc_cv_as_mips_explicit_relocs_pcrel
only, while gcc_cv_as_mips_explicit_relocs is used by later code.

Maybe, it is time for use to set gcc_cv_as_mips_explicit_relocs always now,
as it has been in Binutils for more than 20 years.

gcc
	* configure.ac: Set gcc_cv_as_mips_explicit_relocs if
	gcc_cv_as_mips_explicit_relocs_pcrel.
	* configure: Regenerate.