HID: core: Add bus define for SoundWire bus

SDCA (SoundWire Device Class for Audio) uses HID to convey
input events from peripheral devices. Add a bus define for the
SoundWire bus to prepare support for this.

Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Signed-off-by: Shuming Fan <shumingf@realtek.com>
Acked-by: Jiri Kosina <jkosina@suse.com>
Link: https://patch.msgid.link/20250616114907.855452-1-shumingf@realtek.com


Signed-off-by: Mark Brown <broonie@kernel.org>