src: Use 'include <string.h>' when appropriate

Drop 'include <string.h>' when it is not used and
add it when it is missing.
Also extra lines removed, or added just before local includes.

Change-Id: Iccac4dbaa2dd4144fc347af36ecfc9747da3de20
Signed-off-by: Elyes HAOUAS <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/31966
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Werner Zeh <werner.zeh@siemens.com>
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>

src/drivers/intel/fsp2_0/notify.c

@@ -14,7 +14,6 @@
 #include <console/console.h>
 #include <cpu/x86/mtrr.h>
 #include <fsp/util.h>
-#include <string.h>
 #include <timestamp.h>
 
 static void fsp_notify(enum fsp_notify_phase phase)

src/drivers/intel/fsp2_0/temp_ram_exit.c

@@ -14,7 +14,6 @@
 #include <fsp/api.h>
 #include <fsp/util.h>
 #include <memrange.h>
-#include <string.h>
 #include <cbfs.h>
 
 void fsp_temp_ram_exit(void)