drm_hwcomposer: Store the HAL_PIXEL_FORMAT_* in the hwc_drm_bo

The new GraphicBufferMapper ImportBuffer takes a format
as an argument, but I believe it wants the HAL_PIXEL_FORMAT_*
and not the DRM_FORMAT value.

So stash the HAL_PIXEL_FORMAT_* into the hwc_drm_bo so we
can pass it along when needed.

Change-Id: Id5b8e0d8c624e26c2c6307f85489665c88a9e75d
Signed-off-by: John Stultz <john.stultz@linaro.org>
diff --git a/drmhwcgralloc.h b/drmhwcgralloc.h
index daa44dc..abfd2c1 100644
--- a/drmhwcgralloc.h
+++ b/drmhwcgralloc.h
@@ -23,7 +23,8 @@
 typedef struct hwc_drm_bo {
   uint32_t width;
   uint32_t height;
-  uint32_t format; /* DRM_FORMAT_* from drm_fourcc.h */
+  uint32_t format;     /* DRM_FORMAT_* from drm_fourcc.h */
+  uint32_t hal_format; /* HAL_PIXEL_FORMAT_* */
   uint32_t usage;
   uint32_t pitches[HWC_DRM_BO_MAX_PLANES];
   uint32_t offsets[HWC_DRM_BO_MAX_PLANES];