firmware: xilinx: Add support to get platform information

Add function to get family code and sub family code from the idcode. This
family code and sub family code helps to identify the platform.
Family code of any platform is on bits 21 to 27 and Sub family code is on
bits 19 and 20.

Signed-off-by: Dhaval Shah <dhaval.r.shah@amd.com>
Signed-off-by: Sai Krishna Potthuri <sai.krishna.potthuri@amd.com>
Reviewed-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/20230731095026.3766675-2-sai.krishna.potthuri@amd.com


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>