For downscaling there is a restriction, the downscaling needed engine
clock can not acceed the real engine clock, and the clock requirement
mostly depend on the specific HW, to solve this problem:
1. Add a pipeline func - downscaling_clk_check for CORE to query the real
   HW if downscaling can be supported.
2. Add new property clock ratio which is the ratio of:
     (mclk << 32) / pxlclk
   then User driver can use this ratio to do the clock check to avoid post
   an invalid downscaling to kernel.

v2: Rebase and Delete debug print
Signed-off-by: James Qian Wang (Arm Technology China) <james.qian.wang@arm.com>
Signed-off-by: Liviu Dudau <liviu.dudau@arm.com>