selftests: ublk: Use ARRAY_SIZE() macro to improve code

Use ARRAY_SIZE() macro while calculating size of an array to improve
code readability and reduce potential sizing errors.
Implement this suggestion given by spatch tool by running
coccinelle script - scripts/coccinelle/misc/array_size.cocci
Follow ARRAY_SIZE() macro usage pattern in ublk.c introduced by,
commit ec120093 ("selftests: ublk: fix ublk_find_tgt()")
wherever appropriate to maintain consistency.

Signed-off-by: Akhilesh Patil <akhilesh@ee.iitb.ac.in>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/aKGihYui6/Pcijbk@bhairav-test.ee.iitb.ac.in


Signed-off-by: Jens Axboe <axboe@kernel.dk>