libfrog: rename XFROG_SCRUB_TYPE_* to XFROG_SCRUB_GROUP_*

libfrog: rename XFROG_SCRUB_TYPE_* to XFROG_SCRUB_GROUP_*

I didn't do a good job of naming XFROG_SCRUB_TYPE when I created that
enumeration.  The goal of the enum is to group the scrub ioctl's
XFS_SCRUB_TYPE_* codes by principal filesystem object (AG, inode, etc.)
but for some dumb reason I chose to reuse "type".  This is confusing,
so fix this sin.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Bill O'Donnell <bodonnel@redhat.com>