xfs: use %px for data pointers when debugging

Starting with commit 57e734423a ("vsprintf: refactor %pK code out of
pointer"), the behavior of the raw '%p' printk format specifier was
changed to print a 32-bit hash of the pointer value to avoid leaking
kernel pointers into dmesg.  For most situations that's good.

This is /undesirable/ behavior when we're trying to debug XFS, however,
so define a PTR_FMT that prints the actual pointer when we're in debug
mode.

Note that %p for tracepoints still prints the raw pointer, so in the
long run we could consider rewriting some of these messages as
tracepoints.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

fs/xfs/libxfs/xfs_dir2_node.c

@@ -1919,7 +1919,7 @@ xfs_dir2_node_addname_int(
 					(unsigned long long)ifbno, lastfbno);
 				if (fblk) {
 					xfs_alert(mp,
-				" fblk %p blkno %llu index %d magic 0x%x",
+				" fblk "PTR_FMT" blkno %llu index %d magic 0x%x",
 						fblk,
 						(unsigned long long)fblk->blkno,
 						fblk->index,