ASoC: fsl: add PPC_MPC52xx dependency to SND_POWERPC_SOC
mpc52xx socs do not define FSL_SOC but need SND_POWERPC_SOC defined to build
ASoC drivers.
Signed-off-by: Eric Millbrandt <emillbrandt@dekaresearch.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>