mb/ocp/deltalake: 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: I0d2c362ba9b494bf4cce280192ec0b91dce3e8bb
Signed-off-by: Elyes HAOUAS <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/50686
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Jonathan Zhang <jonzhang@fb.com>

src/mainboard/ocp/deltalake/ipmi.c

@@ -5,7 +5,6 @@
 #include <drivers/ipmi/ipmi_ops.h>
 #include <drivers/ipmi/ocp/ipmi_ocp.h>
 #include <drivers/vpd/vpd.h>
-#include <string.h>
 
 #include "ipmi.h"
 #include "vpd.h"

src/mainboard/ocp/deltalake/loglevel_vpd.c

@@ -2,7 +2,6 @@
 
 #include <console/console.h>
 #include <drivers/vpd/vpd.h>
-#include <string.h>
 
 #include "vpd.h"
 

src/mainboard/ocp/deltalake/romstage.c

@@ -7,7 +7,6 @@
 #include <fsp/api.h>
 #include <FspmUpd.h>
 #include <soc/romstage.h>
-#include <string.h>
 
 #include "chip.h"
 #include "ipmi.h"