ext4: combine ext4_handle_error() and save_error_info()

save_error_info() is always called together with ext4_handle_error().
Combine them into a single call and move unconditional bits out of
save_error_info() into ext4_handle_error().

Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20201216101844.22917-2-jack@suse.cz


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