soc/intel/apollolake: pre-evaluate gpio number values

To allow sharing macros in ASL as well as C the macros can't
have complex expression because the ASL compiler does not
evaluate those expressions. To that end, just pre-calculate
the values. Lastly, add N_OFFSET and utilize it for symmetry.

Change-Id: I546d71008e776b27ce8bcd24d2cbd2ee1b2d8020
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/13693
Tested-by: build bot (Jenkins)
Reviewed-by: Martin Roth <martinroth@google.com>

src/soc/intel/apollolake/gpio.c

@@ -29,7 +29,7 @@ static const struct pad_community {
 		.first_pad = NW_OFFSET,
 	}, {
 		.port = GPIO_NORTH,
-		.first_pad = 0,
+		.first_pad = N_OFFSET,
 	}
 };