[GFS2] Update ioctl() to new interface

This is designed as a fs independent way to set flags on a
particular inode. The values of the ioctl() and flags are
designed to be identical to the ext2/3 values. Assuming that
this plan is acceptable to people in general, the plan is to
then move other fs across to using the same set of #defines,
etc.

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