xfs: remove impossible condition

bp_release is set to 0 just before the breakpoint of the for loop before
the conditional check (in line 458). The other breakpoint is a goto that
skips the dead code.

Addresses-Coverity-Id: 102338

Signed-off-by: Luis de Bethencourt <luisbg@osg.samsung.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Chinner <david@fromorbit.com>