firmware: xilinx: Add zynqmp_pm_get_chipid() API

This patch adds a new API to provide access to the
hardware related data like soc revision, IDCODE... etc.

Signed-off-by: Nava kishore Manne <nava.manne@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>