ALSA: tea6330t: add mixer state restore helper

ALSA: tea6330t: add mixer state restore helper

The InterWave STB variant uses a TEA6330T mixer on its private
I2C bus. The mixer state is cached in software, but there is no
helper to push that register image back to hardware after system
resume.

Add a small restore helper that reapplies the cached TEA6330T
register image to the device so board drivers can restore the
external mixer state as part of their PM resume path.

Take snd_i2c_lock() around the full device lookup and restore
sequence so the bus device list traversal is also protected.

Signed-off-by: Cássio Gabriel <cassiogabrielcontato@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Link: https://patch.msgid.link/20260407-alsa-interwave-pm-v2-2-8dd96c6129e9@gmail.com