Input: ALPS - clean up code for SS5 hardware

The return value of alps_get_pkt_id_ss4_v2() should really be "enum
SS4_PACKET_ID", not "unsigned char".  Correct this.

Also, most of the Alps SS5 (SS4 v2) packet byte parsing code is implemented
using macros, but there are a few places where bytes are directly
manipulated in alps.c.  For consistency, migrate the rest of these to
macros.

Reviewed-by: Pali Rohár <pali.rohar@gmail.com>
Signed-off-by: Paul Donohue <linux-kernel@PaulSD.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>