gfs2_file_splice_read() f_op grabs and releases the cluster-wide
inode glock to sync the inode size to the latest.

Without this, generic_file_splice_read() uses an older i_size value
and can return EOF for valid offsets in the inode.
Signed-off-by: NAbhi Das <adas@redhat.com>
Signed-off-by: NBob Peterson <rpeterso@redhat.com>