[GFS2] Update GFS2 for the recent pull from Linus

Some interfaces have changed. In particular one of the posix
locking functions has changed prototype, along with the
address space operation invalidatepage and the block getting
callback to the direct IO function.

In addition add the splice file operations. These will need to
be updated to support AOP_TRUNCATED_PAGE before they will be
of much use to us.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>