sb/intel/*/lpc: 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: I8f8655853fd1fc1f3679a4549fdaa08702f96c7b
Signed-off-by: Elyes HAOUAS <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/50684
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>

src/southbridge/intel/i82801gx/lpc.c

@@ -15,7 +15,6 @@
 #include <cpu/x86/smm.h>
 #include <acpi/acpigen.h>
 #include <arch/smp/mpspec.h>
-#include <string.h>
 #include <southbridge/intel/common/acpi_pirq_gen.h>
 #include <southbridge/intel/common/hpet.h>
 #include <southbridge/intel/common/pmbase.h>

src/southbridge/intel/i82801ix/lpc.c

@@ -14,7 +14,6 @@
 #include <acpi/acpi.h>
 #include <cpu/x86/smm.h>
 #include <acpi/acpigen.h>
-#include <string.h>
 #include "chip.h"
 #include "i82801ix.h"
 #include <southbridge/intel/common/pciehp.h>

src/southbridge/intel/i82801jx/lpc.c

@@ -15,7 +15,6 @@
 #include <cpu/x86/smm.h>
 #include <acpi/acpigen.h>
 #include <arch/smp/mpspec.h>
-#include <string.h>
 #include "chip.h"
 #include "i82801jx.h"
 #include <southbridge/intel/common/pciehp.h>

src/southbridge/intel/ibexpeak/lpc.c

@@ -15,7 +15,6 @@
 #include <acpi/acpi.h>
 #include <elog.h>
 #include <acpi/acpigen.h>
-#include <string.h>
 #include <cpu/x86/smm.h>
 #include "chip.h"
 #include "pch.h"

src/southbridge/intel/lynxpoint/lpc.c

@@ -12,7 +12,6 @@
 #include <arch/ioapic.h>
 #include <acpi/acpi.h>
 #include <cpu/x86/smm.h>
-#include <string.h>
 #include "chip.h"
 #include "iobp.h"
 #include "pch.h"