hwmon: (pmbus/ltc2978): Add support for LTC2978A

Detect LTC2978A chip ID. Treat it as LC2978.
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

Documentation/hwmon/ltc2978

@@ -10,10 +10,11 @@ Supported chips:
     Prefix: 'ltc2977'
     Addresses scanned: -
     Datasheet: http://www.linear.com/product/ltc2977
-  * Linear Technology LTC2978
+  * Linear Technology LTC2978, LTC2978A
     Prefix: 'ltc2978'
     Addresses scanned: -
     Datasheet: http://www.linear.com/product/ltc2978
+    	       http://www.linear.com/product/ltc2978a
   * Linear Technology LTC3880
     Prefix: 'ltc3880'
     Addresses scanned: -

drivers/hwmon/pmbus/ltc2978.c

@@ -57,6 +57,7 @@ enum chips { ltc2974, ltc2977, ltc2978, ltc3880, ltc3883 };
 #define LTC2977_ID			0x0130
 #define LTC2978_ID_REV1			0x0121
 #define LTC2978_ID_REV2			0x0122
+#define LTC2978A_ID			0x0124
 #define LTC3880_ID			0x4000
 #define LTC3880_ID_MASK			0xff00
 #define LTC3883_ID			0x4300
@@ -397,7 +398,8 @@ static int ltc2978_probe(struct i2c_client *client,
 		data->id = ltc2974;
 	} else if (chip_id == LTC2977_ID) {
 		data->id = ltc2977;
-	} else if (chip_id == LTC2978_ID_REV1 || chip_id == LTC2978_ID_REV2) {
+	} else if (chip_id == LTC2978_ID_REV1 || chip_id == LTC2978_ID_REV2 ||
+		   chip_id == LTC2978A_ID) {
 		data->id = ltc2978;
 	} else if ((chip_id & LTC3880_ID_MASK) == LTC3880_ID) {
 		data->id = ltc3880;