mb: remove test-only HWIDs

The CONFIG_GBB_HWID can be generated automatically now so we can remove
the test-only HWIDs set in board config files.

BUG=b:140067412
TEST=Built few boards (kukui, cheza, octopus) and checked HWID:
     futility gbb -g coreboot.rom

Change-Id: I4070f09d29c5601dff1587fed8c60714eb2558b7
Signed-off-by: Hung-Te Lin <hungte@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/35635
Reviewed-by: Paul Fagerburg <pfagerburg@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/mainboard/intel/kunimitsu/Kconfig

@@ -69,11 +69,6 @@ config INCLUDE_NHLT_BLOBS
 	select NHLT_NAU88L25
 	select NHLT_SSM4567
 
-config GBB_HWID
-	string
-	depends on CHROMEOS
-	default "KUNIMITSU TEST 8819"
-
 config UART_FOR_CONSOLE
 	int
 	default 2