btrfs: use memparse

Use memparse() instead of its own private implementation.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: linux-btrfs@vger.kernel.org
Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 9213d39..363e209 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -776,7 +776,7 @@
 			mod = 1;
 			sizestr++;
 		}
-		new_size = btrfs_parse_size(sizestr);
+		new_size = memparse(sizestr, NULL);
 		if (new_size == 0) {
 			ret = -EINVAL;
 			goto out_unlock;