x86: coreboot: Show the BIOS date

The BIOS version may not be present, e.g. on a Chrome OS build. Add the
BIOS date as well, so we get some sort of indication of coreboot's
vintage.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

board/coreboot/coreboot/coreboot.c

@@ -37,6 +37,7 @@ int show_board_info(void)
 		goto fallback;
 
 	const char *bios_ver = smbios_string(bios, t0->bios_ver);
+	const char *bios_date = smbios_string(bios, t0->bios_release_date);
 	const char *model = smbios_string(system, t1->product_name);
 	const char *manufacturer = smbios_string(system, t1->manufacturer);
 
@@ -46,6 +47,8 @@ int show_board_info(void)
 	printf("Vendor: %s\n", manufacturer);
 	printf("Model: %s\n", model);
 	printf("BIOS Version: %s\n", bios_ver);
+	if (bios_date)
+		printf("BIOS date: %s\n", bios_date);
 
 	return 0;