ASoC: imx-mc13783: Make SND_SOC_IMX_MC13783 visible again

Commit 02502da4

 (ASoC: imx-mc13783: Depend on ARCH_ARM) introduced 'ARCH_ARM'
as a dependency for SND_SOC_IMX_MC13783, but this is a non-existent symbol.

This makes the selection of SND_SOC_IMX_MC13783 to be impossible.

Use the correct 'ARM' symbol instead.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Mark Brown <broonie@linaro.org>