ASoC: fsl: Fix config name of CONFIG_ARCH_MXC

CONFIG_ARCH_MXC should be ARCH_MXC

Fixes: 674226db ("ASoC: fsl: SND_SOC_FSL_AUD2HTX should depend on ARCH_MXC")
Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
Link: https://lore.kernel.org/r/1606371293-29099-1-git-send-email-shengjiu.wang@nxp.com


Signed-off-by: Mark Brown <broonie@kernel.org>