serial: 8250: Disable UART_IER_RLSI and UART_IER_RDI for dma receive

serial: 8250: Disable UART_IER_RLSI and UART_IER_RDI for dma receive

For rockchip serial, received data available and character timeout
interrupts are both enabled by IER[0]. Then when there is data in
the FIFO, received data available interrupt will occurd frequently.
So we must disable it, but which may disable the character timeout
interrput. Then it is useful to add a timer to report the data received
in dma buffer every 10 microsecond.

Change-Id: I1cf9dee495453d3530ab66c95a4e4cfef46b7795
Signed-off-by: Huibin Hong <huibin.hong@rock-chips.com>