define MAP_SYNC on powerpc/powerpc64

Linux defines MAP_SYNC on powerpc and powerpc64 as of commit
22fcea6f85f2 ("mm: move MAP_SYNC to asm-generic/mman-common.h"),
so we can stop undefining it on those architectures.

arch/powerpc/bits/mman.h

@@ -4,7 +4,6 @@
 #define MAP_NORESERVE   0x40
 #undef MAP_LOCKED
 #define MAP_LOCKED	0x80
-#undef MAP_SYNC
 
 #undef MCL_CURRENT
 #define MCL_CURRENT     0x2000

arch/powerpc64/bits/mman.h

@@ -4,7 +4,6 @@
 #define MAP_NORESERVE   0x40
 #undef MAP_LOCKED
 #define MAP_LOCKED	0x80
-#undef MAP_SYNC
 
 #undef MCL_CURRENT
 #define MCL_CURRENT     0x2000