drivers/intel/gma/opregion: Use CBFS cache to load VBT

Thanks to x86 CBFS cache support, we can leverage cbfs_map() function
to load the VBT binary regardless of if it is compressed or not.

Change-Id: I1e37e718a71bd85b0d7dee1efc4c0391798f16f7
Signed-off-by: Jeremy Compostella <jeremy.compostella@intel.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/77886
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>

src/soc/intel/jasperlake/Kconfig

@@ -174,10 +174,6 @@ config SOC_INTEL_COMMON_LPSS_UART_CLK_N_VAL
 	hex
 	default 0xc35
 
-config VBT_DATA_SIZE_KB
-	int
-	default 9
-
 config VBOOT
 	select VBOOT_MUST_REQUEST_DISPLAY
 	select VBOOT_STARTS_IN_BOOTBLOCK