xfs: refactor quota expiration timer modification

xfs: refactor quota expiration timer modification

Source kernel commit: 11d8a9190275855f79d62093d789e962cc7228fb

Define explicit limits on the range of quota grace period expiration
timeouts and refactor the code that modifies the timeouts into helpers
that clamp the values appropriately.  Note that we'll refactor the
default grace period timer separately.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Allison Collins <allison.henderson@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>