mb/google/herobrine: Initialize `pins` to fix the compilation issue

Fix compilation issue introduced with commit 8b63dac0
(google/herobrine: configure gpio to detect board ID) by initialising
the gpio pins.

Signed-off-by: Subrata Banik <subratabanik@google.com>
Change-Id: I084fec777b56f402efb3b04a1d358cd5b0891846
Reviewed-on: https://review.coreboot.org/c/coreboot/+/60784
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: EricR Lai <ericr_lai@compal.corp-partner.google.com>
Reviewed-by: Patrick Georgi <patrick@coreboot.org>

src/mainboard/google/herobrine/boardid.c

@@ -10,7 +10,7 @@
 uint32_t board_id(void)
 {
 	static uint32_t id = UNDEFINED_STRAPPING_ID;
-	gpio_t pins[3];
+	gpio_t pins[3] = { 0 };
 	if (CONFIG(BOARD_GOOGLE_HEROBRINE)) {
 		pins[2] = GPIO(75);
 		pins[1] = GPIO(74);