ASoC: nuc900: export nuc900_ac97_data

The symbol "nuc900_ac97_data" is used by the nuc900_pcm driver,
which may be a loadable module, so we should export it.

If one tries to build SND_SOC_NUC900 without SND_SOC_NUC900_AC97,
the kernel fails to link because of the reference to nuc900_ac97_data.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Xia Kaixu <kaixu.xia@linaro.org>
Signed-off-by: Mark Brown <broonie@linaro.org>