HID: fix hid_ignore_special_drivers module parameter

hid_ignore_special_drivers works fine until hid_scan_report autodetects and
reassign devices (for hid-multitouch, hid-microsoft and hid-rmi).

Simplify the handling of the parameter: if it is there, use hid-generic, no
matter what, and if not, scan the device or rely on the hid_have_special_driver
table.

This was detected while trying to disable hid-multitouch on a Surface Pro cover
which prevented to use the keyboard.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
CC: stable@vger.kernel.org
Signed-off-by: Jiri Kosina <jkosina@suse.cz>