ASoC: mediatek: mt8188: avoid uninitialized variable use

ASoC: mediatek: mt8188: avoid uninitialized variable use

The 'msk' variable has no initialization:

sound/soc/mediatek/mt8188/mt8188-dai-dmic.c:311:4: error: variable 'msk' is uninitialized when used here [-Werror,-Wuninitialized]
  311 |                         msk |= PWR2_TOP_CON1_DMIC_FIFO_SOFT_RST_EN(i);
      |                         ^~~

Set it to zero before the loop.

Fixes: c1e42ec04197 ("ASoC: mediatek: mt8188: Add support for DMIC")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
Link: https://patch.msgid.link/20250227131939.1040168-1-arnd@kernel.org
Signed-off-by: Mark Brown <broonie@kernel.org>