ext4: use is_power_of_2 helper in ext4_mb_regular_allocator

Use intuitive is_power_of_2 helper in ext4_mb_regular_allocator.

Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Link: https://lore.kernel.org/r/20230801143204.2284343-5-shikemeng@huaweicloud.com


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