tree: Remove unused <string.h>

Change-Id: I9ed1a82fcd3fc29124ddc406592bd45dc84d4628
Signed-off-by: Elyes Haouas <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/82666
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Yu-Ping Wu <yupingso@google.com>
Reviewed-by: Yidi Lin <yidilin@google.com>

src/console/vsprintf.c

@@ -2,7 +2,6 @@
 
 #include <console/vtxprintf.h>
 #include <stdio.h>
-#include <string.h>
 
 struct vsnprintf_context {
 	char *str_buf;