hwmon: Add xgene hwmon driver

This patch adds hardware temperature and power reading support for
APM X-Gene SoC using the mailbox communication interface.

Signed-off-by: Hoan Tran <hotran@apm.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/Makefile

@@ -165,6 +165,7 @@ obj-$(CONFIG_SENSORS_W83L785TS)	+= w83l785ts.o
 obj-$(CONFIG_SENSORS_W83L786NG)	+= w83l786ng.o
 obj-$(CONFIG_SENSORS_WM831X)	+= wm831x-hwmon.o
 obj-$(CONFIG_SENSORS_WM8350)	+= wm8350-hwmon.o
+obj-$(CONFIG_SENSORS_XGENE)	+= xgene-hwmon.o
 
 obj-$(CONFIG_PMBUS)		+= pmbus/