powerpc: Drop _nmask_and_or_msr()

_nmask_and_or_msr() is only used at two places to set MSR_IP.

The SYNC is unnecessary as the users are not PowerPC 601.

Can be easily writen in C.

Do it, and drop _nmask_and_or_msr()

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/c2d2b8dfb8dd677026b26dffc8d31070c38a6b89.1597388079.git.christophe.leroy@csgroup.eu

arch/powerpc/kernel/misc_32.S

@@ -215,19 +215,6 @@ _GLOBAL(low_choose_7447a_dfs)
 
 #endif /* CONFIG_CPU_FREQ_PMAC && CONFIG_PPC_BOOK3S_32 */
 
-/*
- * complement mask on the msr then "or" some values on.
- *     _nmask_and_or_msr(nmask, value_to_or)
- */
-_GLOBAL(_nmask_and_or_msr)
-	mfmsr	r0		/* Get current msr */
-	andc	r0,r0,r3	/* And off the bits set in r3 (first parm) */
-	or	r0,r0,r4	/* Or on the bits in r4 (second parm) */
-	SYNC			/* Some chip revs have problems here... */
-	mtmsr	r0		/* Update machine state */
-	isync
-	blr			/* Done */
-
 #ifdef CONFIG_40x
 
 /*