serial: test: update selected symbols

Pretend that the serial test driver supports the interrupt and async
API's, as these can be required for various drivers. Also select
`SERIAL_HAS_DRIVER` so that the serial library will be included.

Signed-off-by: Jordan Yates <[email protected]>

Author: Jordan Yates

drivers/serial/Kconfig.test

@@ -6,3 +6,6 @@ DT_COMPAT_VND_SERIAL := vnd,serial
 # Hidden option to enable the vnd,serial dummy driver used in testing.
 config SERIAL_TEST
 	def_bool $(dt_compat_enabled,$(DT_COMPAT_VND_SERIAL))
+	select SERIAL_HAS_DRIVER
+	select SERIAL_SUPPORT_INTERRUPT
+	select SERIAL_SUPPORT_ASYNC