drm_hwcomposer: Move platform-specific importer headers

Now that importer.h is platform.h, move the platform-specific
headers to match.

BUG=b/28117135
TEST=compiles

Change-Id: I08563505b77529257892841845ef4117d2992bb0
Signed-off-by: Sean Paul <seanpaul@chromium.org>
4 files changed