src/mainboard: Remove unused <stdlib.h>

Found using:
diff <(git grep -l '#include <stdlib.h>' -- src/) <(git grep -l 'memalign(\|malloc(\|calloc(\|free(' -- src/)

Change-Id: Ibc594dc6904b26842cf007884ad1913f99a337f2
Signed-off-by: Elyes HAOUAS <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/60618
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>

src/mainboard/google/zork/variants/baseboard/gpio_baseboard_dalboz.c

@@ -5,7 +5,6 @@
 #include <gpio.h>
 #include <soc/gpio.h>
 #include <soc/smi.h>
-#include <stdlib.h>
 #include <variant/gpio.h>
 
 static const struct soc_amd_gpio gpio_set_stage_ram[] = {

src/mainboard/google/zork/variants/baseboard/gpio_baseboard_trembyle.c

@@ -7,7 +7,6 @@
 #include <gpio.h>
 #include <soc/gpio.h>
 #include <soc/smi.h>
-#include <stdlib.h>
 #include <variant/gpio.h>
 
 static const struct soc_amd_gpio gpio_set_stage_ram[] = {

src/mainboard/lippert/frontrunner-af/variants/frontrunner-af/mainboard.c

@@ -1,6 +1,5 @@
 /* SPDX-License-Identifier: GPL-2.0-only */
 
-#include <stdlib.h>
 #include <amdblocks/acpimmio.h>
 #include <amdblocks/acpimmio_legacy_gpio100.h>
 #include <console/console.h>

src/mainboard/lippert/frontrunner-af/variants/toucan-af/mainboard.c

@@ -1,6 +1,5 @@
 /* SPDX-License-Identifier: GPL-2.0-only */
 
-#include <stdlib.h>
 #include <amdblocks/acpimmio.h>
 #include <amdblocks/acpimmio_legacy_gpio100.h>
 #include <console/console.h>