Fix some typo and brain twister logical.

Fix some typo and brain twister logical.

gcc/
	* config/mips/mips.c: Fix typo in documentation of
	mips_loongson_ext2_prefetch_cookie.
	(mips_option_override): fix brain twister logical.
	* config/mips/mips.h: Fix typo in documentation of
	ISA_HAS_CTZ_CTO and define pattern.
	* config/mips/mips.md (prefetch): Hoist EXT2 above
	the 2EF/EXT block.
	(prefetch_indexed): Hoist EXT2 above the EXT block.

gcc/testsuite/
	* gcc.target/mips/loongson-ctz.c: Fix typo.
	* gcc.target/mips/loongson-dctz.c: Fix typo.

From-SVN: r265871