bo: Refactor bo allocation layer to support both exynos and rockchip

Extract common interfaces in src/omap_dumb.c, implmented abstraction
layer in bo.h, and move driver specific parts to bo_exynos.c and
bo_rockchip.c

BUG=chrome-os-partner:29594
TEST=emerge xf86-video-armsoc

Change-Id: I3a3a72ff2eb589094128d841097055931a8d0c0e
Reviewed-on: https://chromium-review.googlesource.com/203587
Reviewed-by: Doug Anderson <dianders@chromium.org>
Commit-Queue: Doug Anderson <dianders@chromium.org>
Tested-by: Doug Anderson <dianders@chromium.org>
7 files changed