xfsprogs: undefined variable fix

xfsprogs: undefined variable fix

Typo fix, which wasn't catch earlier due to #ifdef branching.  The
'rmnttomname' does not exists anywhere and looks like a hybrid between
rmntfromname and rmntonname. And because the previous if has has
'fromname' on both arguments of realpath, I choose the same approach
when fixing it.

Signed-off-by: Jan Tulak <jtulak@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Chinner <david@fromorbit.com>