xilinx: common: Add function to print SoC info

Add print_cpuinfo() to print SoC info like family & revision.
This function depends on CONFIG_DISPLAY_CPUINFO config.

Signed-off-by: T Karthik Reddy <t.karthik.reddy@xilinx.com>
Reviewed-by: Ashok Reddy Soma <ashok.reddy.soma@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>