HID: alps: Separate U1 device code

Create 'static int u1_init()' and factor out U1 device initialization code from
main initialization and introduce per-device 'has_sp' flag.

[jkosina@suse.cz: rewrite changelog]
Signed-off-by: Masaki Ota <masaki.ota@jp.alps.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>