ext4: Move overlap assert logic into a separate function

Abstract out the logic to double check for overlaps in normalize_pa to
a separate function. Since there has been no reports in past where we
have seen any overlaps which hits this bug_on(), in future we can
consider calling this function under "#ifdef AGGRESSIVE_CHECK" only.

There are no functional changes in this patch

Signed-off-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/35dd5d94fa0b2d1cd2d2947adf8967279c72967d.1679731817.git.ojaswin@linux.ibm.com


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