quota: kill the vfs_dq_off and vfs_dq_quota_on_remount wrappers

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: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index fb1e191..08d3110 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3631,11 +3631,9 @@
 		}
 
 		if (*flags & MS_RDONLY) {
-			err = vfs_dq_off(sb, 1);
-			if (err < 0 && err != -ENOSYS) {
-				err = -EBUSY;
+			err = dquot_suspend(sb, -1);
+			if (err < 0)
 				goto restore_opts;
-			}
 
 			/*
 			 * First of all, the unconditional stuff we have to do
@@ -3722,7 +3720,7 @@
 	unlock_super(sb);
 	unlock_kernel();
 	if (enable_quota)
-		vfs_dq_quota_on_remount(sb);
+		dquot_resume(sb, -1);
 	return 0;
 
 restore_opts: