ALSA: scarlett2: Add device_setup option to use FCP driver

ALSA: scarlett2: Add device_setup option to use FCP driver

Add a new device_setup option (SCARLETT2_USE_FCP_DRIVER = 0x08) that
allows users to opt in to using the new FCP driver instead of the
existing scarlett2 driver for their device. This provides a way to
test the new FCP driver on existing supported hardware while keeping
the Scarlett2 driver as the default.

When the SCARLETT2_USE_FCP_DRIVER bit is set in device_setup, the
scarlett2 driver initialisation will hand off to the FCP driver
instead of proceeding with its own initialisation. The FCP driver then
provides access to the device via its hwdep interface.

Signed-off-by: Geoffrey D. Bennett <g@b4.vu>
Link: https://patch.msgid.link/94ffd7971d73cb0cbea6933b28f7528ce5b9edde.1737048528.git.g@b4.vu
Signed-off-by: Takashi Iwai <tiwai@suse.de>