Instead of having wrappers in the VFS namespace export the dquot_suspend
and dquot_resume helpers directly.  Also rename vfs_quota_disable to
dquot_disable while we're at it.

[Jan Kara: Moved dquot_suspend to quotaops.h and made it inline]
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJan Kara <jack@suse.cz>