tty: xilinx_uartps: Check clk_enable return value

If clocks are not enabled the register access may hang the system.
Check for the clock enable return value and bail out if not enabled.

Signed-off-by: Shubhrajyoti Datta <shubhrajyoti.datta@xilinx.com>
Link: https://lore.kernel.org/r/20220729114748.18332-2-shubhrajyoti.datta@xilinx.com


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