Change kAllocatorSpace for powerpc64.
Fixes issue:
@@ -125,7 +125,7 @@ const uptr kAllocatorSpace = ~(uptr)0;
const uptr kAllocatorSize = 0x40000000000ULL; // 4T.
typedef DefaultSizeClassMap SizeClassMap;
# elif defined(__powerpc64__)
-const uptr kAllocatorSpace = 0xa0000000000ULL;
+const uptr kAllocatorSpace = ~(uptr)0;
const uptr kAllocatorSize = 0x20000000000ULL; // 2T.
typedef DefaultSizeClassMap SizeClassMap;
# elif defined(__aarch64__) && SANITIZER_ANDROID
