Driver core clears the driver data to NULL after device_release
or on probe failure, so just remove it from here.
Driver core change:
"device-core: Ensure drvdata = NULL when no driver is bound"
(sha1: 
0998d0631001288a5974afc0b2a5f568bcdecb4d)
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
        amba_set_drvdata(dev, uap);
        ret = uart_add_one_port(&amba_reg, &uap->port);
        if (ret) {
-               amba_set_drvdata(dev, NULL);
                amba_ports[i] = NULL;
                clk_put(uap->clk);
  unmap:
        struct uart_amba_port *uap = amba_get_drvdata(dev);
        int i;
 
-       amba_set_drvdata(dev, NULL);
-
        uart_remove_one_port(&amba_reg, &uap->port);
 
        for (i = 0; i < ARRAY_SIZE(amba_ports); i++)
 
        amba_set_drvdata(dev, uap);
        ret = uart_add_one_port(&amba_reg, &uap->port);
        if (ret) {
-               amba_set_drvdata(dev, NULL);
                amba_ports[i] = NULL;
                pl011_dma_remove(uap);
        }
        struct uart_amba_port *uap = amba_get_drvdata(dev);
        int i;
 
-       amba_set_drvdata(dev, NULL);
-
        uart_remove_one_port(&amba_reg, &uap->port);
 
        for (i = 0; i < ARRAY_SIZE(amba_ports); i++)