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/ext2/super.c b/fs/ext2/super.c
index 73346de..318ebc5 100644
--- a/fs/ext2/super.c
+++ b/fs/ext2/super.c
@@ -1250,9 +1250,8 @@
 		es->s_mtime = cpu_to_le32(get_seconds());
 		spin_unlock(&sbi->s_lock);
 
-		err = vfs_dq_off(sb, 1);
-		if (err < 0 && err != -ENOSYS) {
-			err = -EBUSY;
+		err = dquot_suspend(sb, -1);
+		if (err < 0) {
 			spin_lock(&sbi->s_lock);
 			goto restore_opts;
 		}
@@ -1281,7 +1280,7 @@
 
 		ext2_write_super(sb);
 
-		vfs_dq_quota_on_remount(sb);
+		dquot_resume(sb, -1);
 	}
 
 	return 0;