ASoC: mchp-spdifrx: Fix uninitialized use of mr in mchp_spdifrx_hw_params()

Clang warns:

  ../sound/soc/atmel/mchp-spdifrx.c:455:3: error: variable 'mr' is uninitialized when used here [-Werror,-Wuninitialized]
                  mr |= SPDIFRX_MR_ENDIAN_BIG;
                  ^~
  ../sound/soc/atmel/mchp-spdifrx.c:432:8: note: initialize the variable 'mr' to silence this warning
          u32 mr;
                ^
                 = 0
  1 error generated.

Zero initialize mr so that these bitwise OR and assignment operation
works unconditionally.

Fixes: fa09fa60 ("ASoC: mchp-spdifrx: fix controls which rely on rsr register")
Link: https://github.com/ClangBuiltLinux/linux/issues/1797Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Link: https://lore.kernel.org/r/20230202-mchp-spdifrx-fix-uninit-mr-v1-1-629a045d7a2f@kernel.orgSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/atmel/mchp-spdifrx.c

@@ -429,7 +429,7 @@ static int mchp_spdifrx_hw_params(struct snd_pcm_substream *substream,
 				  struct snd_soc_dai *dai)
 {
 	struct mchp_spdifrx_dev *dev = snd_soc_dai_get_drvdata(dai);
-	u32 mr;
+	u32 mr = 0;
 	int ret;
 
 	dev_dbg(dev->dev, "%s() rate=%u format=%#x width=%u channels=%u\n",