ext4: fix wrong unit use in ext4_mb_clear_bb

ext4: fix wrong unit use in ext4_mb_clear_bb

commit 247c3d214c23dfeeeb892e91a82ac1188bdaec9f upstream.

Function ext4_issue_discard need count in cluster. Pass count_clusters
instead of count to fix the mismatch.

Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: stable@kernel.org
Reviewed-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Link: https://lore.kernel.org/r/20230603150327.3596033-11-shikemeng@huaweicloud.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>