Bluetooth: Add MacBookAir4,1 support

This patch against current git adds the hardware ID for the Apple
MacBookAir4,1, released in July 2011. The device features a BCM2046
USB chip. The patch was inspired by the previous modifications adding
support for the MacBookAir3,x.

Signed-off-by: Pieter-Augustijn Van Malleghem <p-a@scarlet.be>
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>

drivers/bluetooth/btusb.c

@@ -72,6 +72,9 @@ static struct usb_device_id btusb_table[] = {
 	/* Apple MacBookAir3,1, MacBookAir3,2 */
 	{ USB_DEVICE(0x05ac, 0x821b) },
 
+	/* Apple MacBookAir4,1 */
+	{ USB_DEVICE(0x05ac, 0x821f) },
+
 	/* Apple MacBookPro8,2 */
 	{ USB_DEVICE(0x05ac, 0x821a) },