Input: ALPS - set DualPoint flag for 74 03 28 devices

Here we introduce logic in alps_identify to set the ALPS_DUALPOINT flag
for touchpad hardware responding to E7 report with 73 03 28, as is found
in the Dell Latitude E7470.

Tested-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Ben Gamari <ben@smart-cactus.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>