V4L/DVB (12403): em28xx: properly reports some em2710 chips

As reported by hermann pitton <hermann-pitton@arcor.de>, some devices
has a different chip id for em2710 (likely the older ones):

em28xx: New device @ 480 Mbps (eb1a:2710, interface 0, class 0)
em28xx #0: Identified as EM2710/EM2750/EM2751 webcam grabber (card=22)
em28xx #0: em28xx chip ID = 17
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/video/em28xx/em28xx-cards.c

@@ -1840,11 +1840,14 @@ void em28xx_pre_card_setup(struct em28xx *dev)
 		dev->chip_id = rc;
 
 		switch (dev->chip_id) {
+		case CHIP_ID_EM2710:
+			em28xx_info("chip ID is em2710\n");
+			break;
 		case CHIP_ID_EM2750:
 			em28xx_info("chip ID is em2750\n");
 			break;
 		case CHIP_ID_EM2820:
-			em28xx_info("chip ID is em2710 or em2820\n");
+			em28xx_info("chip ID is em2820 (or em2710)\n");
 			break;
 		case CHIP_ID_EM2840:
 			em28xx_info("chip ID is em2840\n");

drivers/media/video/em28xx/em28xx-reg.h

@@ -176,7 +176,8 @@
 
 /* FIXME: Need to be populated with the other chip ID's */
 enum em28xx_chip_id {
-	CHIP_ID_EM2820 = 18,	/* Also used by em2710 */
+	CHIP_ID_EM2710 = 17,
+	CHIP_ID_EM2820 = 18,	/* Also used by some em2710 */
 	CHIP_ID_EM2840 = 20,
 	CHIP_ID_EM2750 = 33,
 	CHIP_ID_EM2860 = 34,