powerpc/32: memset(0): use cacheable_memzero

cacheable_memzero uses dcbz instruction and is more efficient than
memset(0) when the destination is in RAM

This patch renames memset as generic_memset, and defines memset
as a prolog to cacheable_memzero. This prolog checks if the byte
to set is 0. If not, it falls back to generic_memcpy()

cacheable_memzero disappears as it is not referenced anywhere anymore
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Scott Wood <scottwood@freescale.com>

arch/powerpc/lib/copy_32.S

@@ -74,9 +74,9 @@ CACHELINE_MASK = (L1_CACHE_BYTES-1)
  * to set them to zero.  This requires that the destination
  * area is cacheable.  -- paulus
  */
-_GLOBAL(cacheable_memzero)
-	mr	r5,r4
-	li	r4,0
+_GLOBAL(memset)
+	cmplwi	r4,0
+	bne-	generic_memset
 	addi	r6,r3,-4
 	cmplwi	0,r5,4
 	blt	7f
@@ -117,7 +117,7 @@ _GLOBAL(cacheable_memzero)
 	bdnz	8b
 	blr
 
-_GLOBAL(memset)
+_GLOBAL(generic_memset)
 	rlwimi	r4,r4,8,16,23
 	rlwimi	r4,r4,16,0,15
 	addi	r6,r3,-4