dragonboard: Drop unsupported hwc.drm properties

The drm_hwcomposer code has changed to use vendor.hwc.drm.* for
the properties values, and thus the values here have gone unused
for awhile.

They seem to be old hold-overs from early db410c development, so
lets just get rid of them.

Reported-by: Nicolas Dechesne <nicolas.dechesne@linaro.org>
Reported-by: Benjamin Li <benl@squareup.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Change-Id: I942c225d0a3f0da2ec8c805996c706af19ebfa37
diff --git a/device-common.mk b/device-common.mk
index 58353b8..4beaf6e 100644
--- a/device-common.mk
+++ b/device-common.mk
@@ -59,8 +59,6 @@
     ro.hardware.gralloc=gbm \
     ro.hardware.hwcomposer=drm \
     debug.sf.no_hw_vsync=1 \
-    hwc.drm.use_framebuffer_target=1 \
-    hwc.drm.use_overlay_planes=0 \
     ro.sf.lcd_density=160 \
     ro.opengles.version=196608 \
     persist.demo.rotationlock=1