mb/{intel,prodrive,protectli}: Remove unused <string.h>

Found using:
diff <(git grep -l '#include <string.h>' -- src/) <(git grep -l 'STRINGIFY\|memcpy\|memmove\|memset\|memcmp\|memchr\|strdup\|strconcat\|strnlen\|strlen\|strchr\|strncpy\|strcpy\|strcmp\|strncmp\|strspn\|strcspn\|strstr\|strtok_r\|strtok\|atol\|strrchr\|skip_atoi\|snprintf' -- src/)|grep '<'

Change-Id: Id2aa085a4762355d9fb1628df40f7b43fbc81fc0
Signed-off-by: Elyes HAOUAS <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/50687
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>

src/mainboard/intel/adlrvp/romstage_fsp_params.c

@@ -5,7 +5,6 @@
 #include <fsp/api.h>
 #include <soc/romstage.h>
 #include <spd_bin.h>
-#include <string.h>
 #include <soc/meminit.h>
 #include <baseboard/variants.h>
 #include "board_id.h"

src/mainboard/prodrive/hermes/mainboard.c

@@ -3,7 +3,6 @@
 #include <acpi/acpigen.h>
 #include <device/device.h>
 #include <intelblocks/pmclib.h>
-#include <string.h>
 #include <types.h>
 #include "variants/baseboard/include/eeprom.h"
 #include "gpio.h"

src/mainboard/protectli/vault_bsw/acpi_tables.c

@@ -4,7 +4,6 @@
 #include <arch/ioapic.h>
 #include <soc/acpi.h>
 #include <soc/nvs.h>
-#include <string.h>
 
 void mainboard_fill_gnvs(struct global_nvs *gnvs)
 {