drm_hwcomposer: Add missing assert.h include

drm_hwcomposer fails to compile on aosp/master due to
assert.h not being included.
This patch fixes this issue.

BUG=None
TEST=make

Change-Id: Icb5d5d8a33c9898a5aefa00c1bdbf29965de62a7
Signed-off-by: Robert Foss <robert.foss@collabora.com>
1 file changed