mb/google: Remove obsolete Kconfig symbol VBT_DATA_SIZE_KB

The symbol VBT_DATA_SIZE_KB was removed in commit 8bde652241 -
"drivers/intel/gma/opregion: Use CBFS cache to load VBT" CB:77886,
however that patch only removed the Kconfig option from the Intel
chipsets, leaving it unused in the mainboards.

Signed-off-by: Martin Roth <gaumless@gmail.com>
Change-Id: Ia29d8d6ec17b172e662ff591849f1668d65f1ff9
Reviewed-on: https://review.coreboot.org/c/coreboot/+/78967
Reviewed-by: Subrata Banik <subratabanik@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Eric Lai <ericllai@google.com>

src/mainboard/google/brox/Kconfig

@@ -149,8 +149,4 @@ config PCIEXP_DEFAULT_MAX_RESIZABLE_BAR_BITS
 	int
 	default 33
 
-config VBT_DATA_SIZE_KB
-	int
-	default 10
-
 endif # BOARD_GOOGLE_BROX_COMMON

src/mainboard/google/brya/Kconfig

@@ -795,8 +795,4 @@ config PCIEXP_DEFAULT_MAX_RESIZABLE_BAR_BITS
 	int
 	default 33
 
-config VBT_DATA_SIZE_KB
-	int
-	default 10 if BOARD_GOOGLE_PIRRHA
-
 endif # BOARD_GOOGLE_BRYA_COMMON