ASoC: mediatek: SND_SOC_MT8195 should depend on ARCH_MEDIATEK

The Mediatek MT8195 sound hardware is only present on Mediatek MT8195
SoCs.  Hence add a dependency on ARCH_MEDIATEK, to prevent asking the
user about this driver when configuring a kernel without Mediatek SoC
support.

Fixes: 6746cc85

 ("ASoC: mediatek: mt8195: add platform driver")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/7e628e359bde04ceb9ddd74a45931059b4a4623c.1630415860.git.geert+renesas@glider.be
Signed-off-by: Mark Brown <broonie@kernel.org>