ext4: make 'abort' mount option handling standard

ext4: make 'abort' mount option handling standard

'abort' mount option is the only mount option that has special handling
and sets a bit in sbi->s_mount_flags. There is not strong reason for
that so just simplify the code and make 'abort' set a bit in
sbi->s_mount_opt2 as any other mount option. This simplifies the code
and will allow us to drop EXT4_MF_FS_ABORTED completely in the following
patch.

Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20230616165109.21695-4-jack@suse.cz
Signed-off-by: Theodore Ts'o <tytso@mit.edu>