Move two functions for initializing & de-initializing backing file
into common.c.
Also move one common helper into kublk.h.
Prepare for supporting ublk-stripe.
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20250322093218.431419-5-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
