xfs: remove the call to xfs_buf_reverify in xfs_trans_read_buf_map

xfs: remove the call to xfs_buf_reverify in xfs_trans_read_buf_map

xfs_trans_read_buf_map asserts bp->b_ops is non-NULL just before
calling xfs_buf_reverify which is a no-op if bp->b_ops is set, making the
call dead code ever since it as added in commit 1aff5696f3e0 ("xfs: always
assign buffer verifiers when one is provided").

Remove the useless call, mark xfs_buf_reverify static and clean up the
branch dealing with a buffer attached to the transaction in a bit by
deduplicating and keeping together the asserts and removing the bip
variable only used once outside of asserts and tracing.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>
Signed-off-by: Carlos Maiolino <cem@kernel.org>