serial: 8250_dw: Allow hardware flow control to be used

serial: 8250_dw: Allow hardware flow control to be used

In the most common use case, the Synopsys DW UART driver does not
set the set_termios callback function.  This prevents UPSTAT_AUTOCTS
from being set when the UART flag CRTSCTS is set.  As a result, the
driver will use software flow control as opposed to hardware flow
control.

To fix the problem, the set_termios callback function is set to the
DW specific function.  The logic to set UPSTAT_AUTOCTS is moved so
that any clock error will not affect setting the hardware flow
control.

Reviewed-by: Scott Branden <[email protected]>
Reviewed-by: Ray Jui <[email protected]>
Signed-off-by: Jason Uy <[email protected]>
Reviewed-by: Kefeng Wang <[email protected]>
Reviewed-by: Andy Shevchenko <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>