ASoC: PXA: Brownstone needs I2C

ASoC: PXA: Brownstone needs I2C

I rand into a new build error with SND_MMP_SOC_BROWNSTONE:

warning: (SND_MMP_SOC_BROWNSTONE && SND_SOC_SAMSUNG_SMDK_WM8994 && SND_SOC_SMDK_WM8994_PCM && SND_SOC_LITTLEMILL) selects MFD_WM8994 which has unmet direct dependencies (HAS_IOMEM && I2C)
drivers/mfd/wm8994-core.c:688:1: error: data definition has no type or storage class [-Werror]
drivers/mfd/wm8994-core.c:688:1: error: type defaults to 'int' in declaration of 'module_i2c_driver' [-Werror=implicit-int]

I don't see why this never showed up before, as the dependency seems to
have been missing since the symbol was first introduced several years
ago. This adds a dependency like the other drivers have.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Mark Brown <broonie@kernel.org>