soc/amd: factor out common AOAC device enable and status query functions

The code on Stoneyridge didn't set the FCH_AOAC_TARGET_DEVICE_STATE bits
to FCH_AOAC_D0_INITIALIZED like the code for Picasso does, but that is
the default value after reset for those bits on both platforms.

Change-Id: I7cae23257ae54da73b713fe88aca5edfa4656754
Signed-off-by: Felix Held <felix-coreboot@felixheld.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/48183
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Marshall Dawson <marshalldawson3rd@gmail.com>

src/soc/amd/picasso/uart.c

@@ -6,6 +6,7 @@
 #include <device/mmio.h>
 #include <amdblocks/gpio_banks.h>
 #include <amdblocks/acpimmio.h>
+#include <amdblocks/aoac.h>
 #include <soc/southbridge.h>
 #include <soc/gpio.h>
 #include <soc/uart.h>