tty: xilinx_uartps: Check the clk_enable return value

Check the clk_enable return value.
If clocks are not enabled the register accesses could hang the
system so error out instead.

Signed-off-by: Shubhrajyoti Datta <shubhrajyoti.datta@xilinx.com>
Link: https://lore.kernel.org/r/20220729114748.18332-8-shubhrajyoti.datta@xilinx.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>