util/macros: Import ALIGN_POT from ralloc.c

v2 (Jason Ekstrand):
 - Rename y to pot_align (Brian)
 - Also use ALIGN_POT in build_id.c and slab.c (Brian)

Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>
Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>
Reviewed-by: Brian Paul <brianp@vmware.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

src/util/ralloc.c

@@ -553,8 +553,6 @@ ralloc_vasprintf_rewrite_tail(char **str, size_t *start, const char *fmt,
  * other buffers.
  */
 
-#define ALIGN_POT(x, y) (((x) + (y) - 1) & ~((y) - 1))
-
 #define MIN_LINEAR_BUFSIZE 2048
 #define SUBALLOC_ALIGNMENT sizeof(uintptr_t)
 #define LMAGIC 0x87b9c7d3