serial: 8250_dw: Add ACPI ID for Intel Braswell

Another new ACPI identifier for the 8250 dw bindings to cover newer Intel
SoCs such as Braswell.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>