generic/745: rework support fs checking

To prepare for deprecating _supported_fs use a case statement and
_notrun.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: David Disseldorp <ddiss@suse.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Zorro Lang <zlang@kernel.org>
1 file changed