serial: xilinx_uartps: return early in cdns_uart_handle_tx()

Return from the true branch of the 'if'. This saves one indentation
level and makes the code more readable.

The two comments about what obvious code does are removed too.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20220421101708.5640-3-jslaby@suse.cz


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