ASoC: codecs: nau8325: Silence uninitialized variables warnings

ASoC: codecs: nau8325: Silence uninitialized variables warnings

clang W=1 builds warn:

  nau8325.c:430:13: error: variable 'n2_max' is uninitialized when used here [-Werror,-Wuninitialized]

which are false positive, because the variables will be always
initialized when used (guarded by mclk_max!=0 check).  However
initializing them upfront makes the code more obvious and easier, plus
it silences the warning.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Link: https://patch.msgid.link/20251203140611.87191-2-krzysztof.kozlowski@oss.qualcomm.com
Signed-off-by: Mark Brown <broonie@kernel.org>