mainboard/facebook/fbg1701: Set CBFS_SIZE to 0x600000

CBFS_SIZE equals size of whole SPI device.
The descriptor and ME need to be placed in bottom part.
Reduce the CBFS_SIZE to maximum avalaible size.

BUG=N/A
TEST=Boot Embedded Linux 4.20 on Facebook FBG-1701

Change-Id: Iecfae4573100c6787b6e8b1c4f2583a7fb3d95a3
Signed-off-by: Frans Hendriks <fhendriks@eltan.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/33484
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
diff --git a/src/mainboard/facebook/fbg1701/Kconfig b/src/mainboard/facebook/fbg1701/Kconfig
index b3c589d..95d8f6c 100644
--- a/src/mainboard/facebook/fbg1701/Kconfig
+++ b/src/mainboard/facebook/fbg1701/Kconfig
@@ -54,7 +54,7 @@
 
 config CBFS_SIZE
 	hex
-	default 0x00800000
+	default 0x00600000
 
 config CPU_MICROCODE_CBFS_LEN
 	hex