drm/fourcc: Add modifier definitions for Arm Fixed Rate Compression

Arm Fixed Rate Compression (AFRC) is a proprietary fixed rate image
compression protocol and format.
It is designed to provide guaranteed bandwidth and memory footprint
reductions in graphics and media use-cases.

This patch aims to add modifier definitions for describing
AFRC.

Signed-off-by: Normunds Rieksts <normunds.rieksts@arm.com>
Reviewed-by: Liviu Dudau <liviu.dudau@arm.com>
Signed-off-by: Liviu Dudau <liviu.dudau@arm.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210701170709.39922-1-normunds.rieksts@arm.com