ALSA: usb - update gfp/slab.h includes

Implicit slab.h inclusion via percpu.h is about to go away.  Make sure
gfp.h or slab.h is included as necessary.
Signed-off-by: NTejun Heo <tj@kernel.org>
Signed-off-by: NTakashi Iwai <tiwai@suse.de>

sound/usb/caiaq/input.c

@@ -16,6 +16,7 @@
  *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
 */
 
+#include <linux/gfp.h>
 #include <linux/init.h>
 #include <linux/usb.h>
 #include <linux/usb/input.h>

sound/usb/urb.c

@@ -15,6 +15,7 @@
  *
  */
 
+#include <linux/gfp.h>
 #include <linux/init.h>
 #include <linux/usb.h>
 #include <linux/usb/audio.h>