mips.c (mips_emit_loadgp): Return early if there is nothing do to...

gcc/
	* config/mips/mips.c (mips_emit_loadgp): Return early if
	there is nothing do to, otherwise emit a blockage if
	!TARGET_EXPLICIT_RELOCS || crtl->profile.
	* config/mips/mips.md (loadgp_blockage): Use SI rather than DI.

From-SVN: r136294