erofs: get rid of check_layout_compatibility()

Simple enough to just open-code it.

Signed-off-by: Hongzhen Luo <hongzhen@linux.alibaba.com>
Reviewed-by: Sandeep Dhavale <dhavale@google.com>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20240806112208.150323-1-hongzhen@linux.alibaba.com


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