Btrfs-progs: update btrfs_file_extent_inline_len to match kernel version

Btrfs-progs: update btrfs_file_extent_inline_len to match kernel version

The following kernel commit changed the definition of the inline function
btrfs_file_extent_inline_len():

    commit 514ac8ad8793a097c0c9d89202c642479d6dfa34
    Author: Chris Mason <clm@fb.com>
    Date:   Fri Jan 3 21:07:00 2014 -0800

    Btrfs: don't use ram_bytes for uncompressed inline items

    If we truncate an uncompressed inline item, ram_bytes isn't updated to reflect
    the new size.  The fixe uses the size directly from the item header when
    reading uncompressed inlines, and also fixes truncate to update the
    size as it goes.

Not having this new definition implies that the restore tool might misbehave when
restoring files with an inline extent that got truncated on a kernel older than
release 3.14.

Signed-off-by: Filipe David Borba Manana <fdmanana@gmail.com>
Signed-off-by: David Sterba <dsterba@suse.cz>