[POWERPC] Fix slb.c compile warnings

Arrange for a syntax check to always be done on the powerpc/mm/slb.c
DBG() macro by defining it to pr_debug() for non-debug builds.

Also, fix these related compile warnings:

  slb.c:273: warning: format '%04x' expects type 'unsigned int', but argument 2 has type 'long unsigned int
  slb.c:274: warning: format '%04x' expects type 'unsigned int', but argument 2 has type 'long unsigned int'

Signed-off-by: Geoff Levand <geoffrey.levand@am.sony.com>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>