drivers/gpio: Fix drivers who are implicit users of module.h

A pending cleanup will mean that module.h won't be implicitly
everywhere anymore.  Make sure the modular drivers in gpio
are actually calling out for <module.h> explicitly in advance.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

drivers/gpio/gpio-pcf857x.c

@@ -23,6 +23,7 @@
 #include <linux/gpio.h>
 #include <linux/i2c.h>
 #include <linux/i2c/pcf857x.h>
+#include <linux/module.h>
 
 
 static const struct i2c_device_id pcf857x_id[] = {