dm integrity: fix error reporting in bitmap mode after creation

The dm-integrity target did not report errors in bitmap mode just after
creation. The reason is that the function integrity_recalc didn't clean up
ic->recalc_bitmap as it proceeded with recalculation.

Fix this by updating the bitmap accordingly -- the double shift serves
to rounddown.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Fixes: 468dfca3

 ("dm integrity: add a bitmap mode")
Cc: stable@vger.kernel.org # v5.2+
Signed-off-by: Mike Snitzer <snitzer@redhat.com>