kernel: don't build modules or dtbs unless enabled

Build modules and dtbs only if enabled. The make commands were allowed to
fail silently to support builds that did not have these options
enabled.

This had a side effect of allowing builds to complete even if modules
failed to build. Don't suppress these error anymore.

Change-Id: I842124b465d9e14edd6a09ffe54f09da32f10632
1 file changed