mfd: ucb1x00: Explicitely include linux/device.h

Fixes this compilation error:
  linux/include/linux/mfd/ucb1x00.h:137:17: error: field 'dev' has incomplete type

Signed-off-by: Andrea Adami <andrea.adami@gmail.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

include/linux/mfd/ucb1x00.h

@@ -10,6 +10,7 @@
 #ifndef UCB1200_H
 #define UCB1200_H
 
+#include <linux/device.h>
 #include <linux/mfd/mcp.h>
 #include <linux/gpio.h>
 #include <linux/mutex.h>