kernel.mk: Split TARGET_ROOT_MODULES

* Somewhere during the recent kernel updates the modules not built in the kernel are
  being built in $(TARGET_OUT)/lib/hardware now.  Accomodate this change.

Signed-off-by: Brandon McAnsh <brandonm@matricom.net>
kernel.mk: Clean up KERNEL_HARDWARE_OUT after mv-select

Signed-off-by: Brandon McAnsh <brandonm@matricom.net>