[WIP] drm_hwcomposer: Add support for Arm Framebuffer Compression (AFBC) modifiers.

One needs to translate the Gralloc buffer flags for AFBC (eg
MALI_GRALLOC_INTFMT_AFBC_BASIC) to the corresponding linux kernel drm modifiers.
This gets passed to libdrm via drmModeAddFB2WithModifiers.

Signed-off-by: Ayan Kumar Halder <ayan.halder@arm.com>

/-- Note for reviewer
I was able to get this working for Android P on Juno with Mali DP650 and Mali
T860 gpu(with some additional hacks). I have not yet validated this hikey960.

I have used the following components:-
1. Gralloc (from https://android.googlesource.com/device/linaro/hikey/+/master/gralloc960)
  - Built with MALI_MMSS=1
2. Libdrm (from git://anongit.freedesktop.org/mesa/drm)
  - You would need drm_fourcc.h and gralloc_handle.h
1 job for ssh-master in 43 seconds (queued for 2 seconds)