aom_mem,align_addr: use ~ to create mask

removes the need for an intermediate cast to int, which was missing in
the call added in:
73a3fd4 aom_mem: Refactor code

quiets a visual studio warning:
C4146: unary minus operator applied to unsigned type, result still
unsigned

Change-Id: I76c4003416759c6c76b78f74de7c0d2ba5071216
diff --git a/aom_mem/aom_mem.c b/aom_mem/aom_mem.c
index 144085f..4514fb5 100644
--- a/aom_mem/aom_mem.c
+++ b/aom_mem/aom_mem.c
@@ -42,7 +42,7 @@
   const size_t aligned_size = GetAlignedMallocSize(size, align);
   void *const addr = malloc(aligned_size);
   if (addr) {
-    x = align_addr((unsigned char *)addr + ADDRESS_STORAGE_SIZE, (int)align);
+    x = align_addr((unsigned char *)addr + ADDRESS_STORAGE_SIZE, align);
     SetActualMallocAddress(x, addr);
   }
   return x;