In cs35l56_hda_read_acpi() do not return if ACPI _SUB is missing.

A missing _SUB means that the driver cannot load a system-specific
firmware, because the firmware is identified by the _SUB. But it can
fallback to a generic firmware. Unfortunately this was being handled
by immediately returning 0, which would skip the remaining ACPI
configuration in cs35l56_hda_read_acpi() and so it would not get the
RESET GPIO.
Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Fixes: 73cfbfa9 ("ALSA: hda/cs35l56: Add driver for Cirrus Logic CS35L56 amplifier")
Link: https://lore.kernel.org/r/20230914152525.20829-1-rf@opensource.cirrus.comSigned-off-by: Takashi Iwai <tiwai@suse.de>