ALSA: usb: qcom: Use guard() for mutex locks
Replace the manual mutex lock/unlock pairs with guard() for code
simplification.
The manual mutex lock/unlock are still left in
handle_uaudio_stream_req() and its callee as they have a bit complex
locking patterns.
Only code refactoring, and no behavior change.
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Link: https://patch.msgid.link/20250829150724.6886-8-tiwai@suse.de