tty: xilinx_uartps: move to arch_initcall for earlier console

move to arch_initcall to get the console up really early, it is
quite helpful for spotting early boot problems.

Signed-off-by: Shubhrajyoti Datta <shubhrajyoti.datta@xilinx.com>
Tested-by: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>