bsdrm: move the bs_drm_open functions into their own module

These functions are generic and useful enough to be exportable as their
own module. For example, I use bs_open_filtered to choose input devices.

TEST=stripe still works
BUG=None

Change-Id: Ia8bad9cb7ffa07e1f6e58fdc5eac23ea47455da3
Reviewed-on: https://chromium-review.googlesource.com/329005
Commit-Ready: Zach Reizner <zachr@chromium.org>
Tested-by: Zach Reizner <zachr@chromium.org>
Reviewed-by: Haixia Shi <hshi@chromium.org>
4 files changed