ext4: do not BUG when INLINE_DATA_FL lacks system.data xattr

A syzbot fuzzed image triggered a BUG_ON in ext4_update_inline_data()
when an inode had the INLINE_DATA_FL flag set but was missing the
system.data extended attribute.

Since this can happen due to a maiciouly fuzzed file system, we
shouldn't BUG, but rather, report it as a corrupted file system.

Add similar replacements of BUG_ON with EXT4_ERROR_INODE() ii
ext4_create_inline_data() and ext4_inline_data_truncate().

Reported-by:  <syzbot+544248a761451c0df72f@syzkaller.appspotmail.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>