AR9344 dual UART enabled under Linux

AR9344 support two uart, the usual debugging serial port is UART0, the driver is using 8250, today because the project needs to enable UART1, the configuration process needs to pay attention to several points

1.9344 Gpio Port is multiplexed, can flexibly configure most of the supported features, need to find two Gpio, configured as UART1_TD and UART1_RD function (if using hardware flow control, need to find two Gpio configured as CTS and RTS)

2. The driver can use AR93XX_UART.C, if not using the hardware CTS and RTS function, need to be configured in the driver to disable hardware flow control, the first debugging is RX receive normal but TX data always send failed, finally in the drive to discover that hardware flow control is enabled

3. Interrupt number is ATH79_MISC_IRQ (6), send and receive are based on interrupt mode

AR9344 dual UART enabled under Linux