ANDROID: GKI: Enable SERIAL_8250_DW

Enable support for designware quirks in the 8250 driver. This could be
built as a module, but if the 8250 earlycon driver is being used, doing
so causes problems at boot. When clk_unused_disable() disables the uart
clocks while the earlycon driver is using them, but before the full
driver loads to take over the clocks, the device will reboot.

This adds a relatively small amount of code to GKI so it should be
harmless, at least until a way is found to split the 8250 earlycon
support from the full driver.

Bug: 183963484
Change-Id: I6e54dfce347f546e954703af083a9c55cf2ddd88
Signed-off-by: Alistair Delva <adelva@google.com>