vboot: Remove hard dependency on MISSING_BOARD_RESET

Having a working board reset is certainly better when you're running
vboot (because otherwise you'll hang when transitioning into recovery
mode), but I don't think it should be strictly required, since it's
still somewhat usable without. This is particularly important for
certain test platforms that don't have a good way to reset but might
still be useful for vboot testing/prototyping.

Change-Id: Ia765f54b6e2e176e2d54478fb1e0839d8cab9849
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/38417
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/security/vboot/Kconfig

@@ -28,7 +28,7 @@ config VBOOT
 	default n
 	select VBOOT_LIB
 	select VBOOT_MOCK_SECDATA if !TPM1 && !TPM2
-	depends on !MISSING_BOARD_RESET
+	depends on 0 = 0  # Must have a 'depends on' or board overrides will break it.
 	help
 	  Enabling VBOOT will use vboot to verify the components of the firmware
 	  (stages, payload, etc).