ext4: Add EXT4_IOC_FSGETXATTR/EXT4_IOC_FSSETXATTR to compat_ioctl

These are backed by 'struct fsxattr' which has the same size on all
architectures.

Signed-off-by: Martijn Coenen <maco@android.com>
Link: https://lore.kernel.org/r/20191227134639.35869-1-maco@android.com


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