ALSA: scarlett2: Default mixer driver to enabled

ALSA: scarlett2: Default mixer driver to enabled

Early versions of this mixer driver did not work on all hardware, so
out of caution the driver was disabled by default and had to be
explicitly enabled with device_setup=1.

Since commit 764fa6e686e0 ("ALSA: usb-audio: scarlett2: Fix device
hang with ehci-pci") no more problems of this nature have been
reported. Therefore, enable the driver by default but provide a new
device_setup option to disable the driver in case that is needed.

- device_setup value of 0 now means "enable" rather than "disable".
- device_setup value of 1 is now ignored.
- device_setup value of 4 now means "disable".

Signed-off-by: Geoffrey D. Bennett <g@b4.vu>
Link: https://lore.kernel.org/r/89600a35b40307f2766578ad1ca2f21801286b58.1694705811.git.g@b4.vu
Signed-off-by: Takashi Iwai <tiwai@suse.de>