apparmor: expose compression level limits in sysfs

Create two new files in apparmor's sysfs:

/sys/kernel/security/apparmor/raw_data_compression_level_min
/sys/kernel/security/apparmor/raw_data_compression_level_max

These correspond to the minimum and maximum zstd compression levels
that can be assigned to the apparmor module parameter
raw_data_compression_level.

Signed-off-by: Jon Tourville <jon.tourville@canonical.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>