xfs: Fix the logic check for all quotas being turned off

During the review of seperate pquota inode patches, David noticed
that the test to detect all quotas being turned off was
incorrect, and hence the block was not freeing all the quota
information.

The check made sense in Irix, but in Linux, quota is turned off
one at a time, which makes the test invalid for Linux.

This problem existed since XFS was ported to Linux.

David suggested to fix the problem by detecting when all quotas are
turned off by checking m_qflags.

Signed-off-by: Chandra Seetharaman <sekharan@us.ibm.com>
Reviewed-by: Ben Myers <bpm@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>