moving changes from qva to generic

1- as system side vendor customization can go to product/system_ext
partition so i think there is no need to keep qva so moving the
changes from qva to generic.

2- adding prebuilts dir for system_ext and product.

Change-Id: I5164a313f7c784e0948ab933dfa6a9581a94b863
199 files changed
tree: 670cdb5012ea9af0259b5f35c7645efc91732020
  1. generic/
  2. SEPolicy.mk