[MIPS] Fix build after b0rked changes to <linux/init.h>.

Commit 312b1485fb509c9bc32eda28ad29537896658cb8 made __INIT_REFOK expand
into .section .section ".ref.text", "ax". Since the assembler doesn't
tolerate stuttering in the source that broke all MIPS builds.

Since with this change Sam downgraded __INIT_REFOK the best fix is to
get replace it by the modern days operator. With MIPS the only user
of __INIT_REFOK and __INITDATA_REFOK (which was equally broken) being
unused anyway these can be deleted but that's subject of a separate
commit.

Signed-off-by: Ralf Baechle <[e-mail]>

arch/mips/kernel/head.S

···
 	j	kernel_entry
 #endif
 
-	__INIT_REFOK
+	__REF
 
 NESTED(kernel_entry, 16, sp)			# kernel entry point