payloads/coreinfo: Use C99 flexible arrays

Use C99 flexible arrays instead of older style of one-element or
zero-length arrays.
It allows the compiler to generate errors when the flexible array does
not occur at the end in the structure.

Change-Id: I17811256b04a17539d3ed77f406892ae77e97515
Signed-off-by: Elyes Haouas <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/76848
Reviewed-by: Felix Singer <service+coreboot-gerrit@felixsinger.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

payloads/coreinfo/bootlog_module.c

@@ -17,7 +17,7 @@ static s32 g_max_cursor_line = 0;
 struct cbmem_console {
 	u32 size;
 	u32 cursor;
-	u8 body[0];
+	u8 body[];
 } __packed;
 
 #define CURSOR_MASK ((1 << 28) - 1)