drm_hwcomposer: Don't compile all importers at once

Choose based on the BoardConfig flags.

I'd like to revert this once drm_gralloc is available
in all working branches.

Change-Id: I171d8f9146bdca0f0671092b8e539031c2f64f0f
Signed-off-by: Sean Paul <seanpaul@chromium.org>
1 file changed