ASoC: PXA: make SND_PXA2XX_SOC_AC97 user-selectable

When building a PXA kernel without legacy board file support,
the AC97 code is not built, so none of the AC97 drivers
can be used.

Add a Kconfig prompt to let users turn it on, and have it
enabled by default.

Cc: Robert Jarzmik <robert.jarzmik@free.fr>
Cc: Liam Girdwood <lgirdwood@gmail.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Jaroslav Kysela <perex@perex.cz>
Cc: Takashi Iwai <tiwai@suse.com>
Cc: alsa-devel@alsa-project.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20230105134622.254560-15-arnd@kernel.orgSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/pxa/Kconfig

@@ -16,7 +16,10 @@ config SND_PXA2XX_AC97
 	tristate
 
 config SND_PXA2XX_SOC_AC97
-	tristate
+	tristate "SoC AC97 support for PXA2xx"
+	depends on SND_PXA2XX_SOC
+	depends on AC97_BUS=n
+	default y
 	select AC97_BUS_NEW
 	select SND_PXA2XX_LIB
 	select SND_PXA2XX_LIB_AC97