mb/intel/ehlcrb: Store vboot VBNV in SPI flash

Signed-off-by: Lean Sheng Tan <sheng.tan@9elements.com>
Change-Id: I0d609f0db475877d0ef1f47ab89c34dccb6e16d9
Reviewed-on: https://review.coreboot.org/c/coreboot/+/64475
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Praveen HP <praveen.hodagatta.pranesh@intel.com>
Reviewed-by: Werner Zeh <werner.zeh@siemens.com>

src/mainboard/intel/elkhartlake_crb/Kconfig

@@ -46,6 +46,7 @@ config VBOOT
 	select VBOOT_ALWAYS_ENABLE_DISPLAY
 	select VBOOT_MOCK_SECDATA if !MAINBOARD_HAS_TPM2
 	select VBOOT_NO_BOARD_SUPPORT
+	select VBOOT_VBNV_FLASH
 
 config UART_FOR_CONSOLE
 	int