soc/intel/apollolake: add assert for pad constraints

Ensure the pads passed into the gpio functions are within
range.

Change-Id: Ic523cbfaf60a46709080347af3a36d6330f9a07c
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/13694
Tested-by: build bot (Jenkins)
Reviewed-by: Martin Roth <martinroth@google.com>

src/soc/intel/apollolake/gpio.c

@@ -10,6 +10,7 @@
  * (at your option) any later version.
  */
 
+#include <assert.h>
 #include <soc/gpio.h>
 #include <soc/iosf.h>
 
@@ -37,6 +38,8 @@ static const struct pad_community *gpio_get_community(uint16_t pad)
 {
 	const struct pad_community *map = gpio_communities;
 
+	assert(pad < TOTAL_PADS);
+
 	while (map->first_pad > pad)
 		map++;