xfs: drop the _safe behavior from the xbitmap foreach macro

It's not safe to edit bitmap intervals while we're iterating them with
for_each_xbitmap_extent.  None of the existing callers actually need
that ability anyway, so drop the safe variable.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>