ARM: pxa: remove CONFIG_SND_PXA2XX_AC97 in pxa_defconfig

The CONFIG_SND_PXA2XX_AC97 driver is for the old AC97 bus implementation,
and conflicts with all the new-style AC97 drivers after the conversion,
so the drivers we want all get turned off.

Not disabling the symbol however does the right thing, and we get
the drivers that are selectively enabled here.

Fixes: 25540f68 ("ASoC: pxa: change ac97 dependencies")
Acked-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>