btrfs: disable various operations on encrypted inodes

btrfs: disable various operations on encrypted inodes

Initially, only normal data extents will be encrypted. This change
forbids various other bits:

- allows reflinking only if both inodes have the same encryption status
- disable inline data on encrypted inodes

Note: The patch was taken from v5 of fscrypt patchset
(https://lore.kernel.org/linux-btrfs/cover.1706116485.git.josef@toxicpanda.com/)
which was handled over time by various people: Omar Sandoval, Sweet Tea
Dorminy, Josef Bacik.

Signed-off-by: Omar Sandoval <osandov@osandov.com>
Signed-off-by: Daniel Vacek <neelx@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ add note ]
Signed-off-by: David Sterba <dsterba@suse.com>