orangefs: fix orangefs df output.

[ Upstream commit 0fdec1b3c9fbb5e856a40db5993c9eaf91c74a83 ]

Orangefs df output is whacky. Walt Ligon suggested this might fix it.
It seems way more in line with reality now...

Signed-off-by: Mike Marshall <hubcap@omnibond.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>