ext4: fix unit mismatch in ext4_mb_new_blocks_simple

The "i" returned from mb_find_next_zero_bit is in cluster unit and we
need offset "block" corresponding to "i" in block unit. Convert "i" to
block unit to fix the unit mismatch.

Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Reviewed-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Link: https://lore.kernel.org/r/20230603150327.3596033-3-shikemeng@huaweicloud.com


Signed-off-by: Theodore Ts'o <tytso@mit.edu>