Tidy up gfs2_unstuffer_page by:
a) Moving it into bmap.c
b) Making it static
c) Calling it directly from gfs2_unstuff_dinode
d) Updating all callers of gfs2_unstuff_dinode due to one less
required argument.
It doesn't change the behaviour at all.
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>