erofs: clean up redundant comment and adjust code alignment

Remove some redundant comments in erofs/super.c, and avoid unncessary
line breaks for cleanup.

Signed-off-by: Ferry Meng <mengferry@linux.alibaba.com>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Link: https://lore.kernel.org/r/20230815094849.53249-1-mengferry@linux.alibaba.com


Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>