powerpc32: small optimisation in flush_icache_range()

Inlining of _dcache_range() functions has shown that the compiler
does the same thing a bit better with one insn less
Signed-off-by: NChristophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: NScott Wood <oss@buserror.net>

arch/powerpc/kernel/misc_32.S

@@ -348,10 +348,9 @@ BEGIN_FTR_SECTION
 	PURGE_PREFETCHED_INS
 	blr				/* for 601, do nothing */
 END_FTR_SECTION_IFSET(CPU_FTR_COHERENT_ICACHE)
-	li	r5,L1_CACHE_BYTES-1
-	andc	r3,r3,r5
+	rlwinm	r3,r3,0,0,31 - L1_CACHE_SHIFT
 	subf	r4,r3,r4
-	add	r4,r4,r5
+	addi	r4,r4,L1_CACHE_BYTES - 1
 	srwi.	r4,r4,L1_CACHE_SHIFT
 	beqlr
 	mtctr	r4