HID: i2c-hid: Fill in physical device providing HID functionality

Currently hid_connect() prints out following when I2C connected HID devices
is connected:

  hid-multitouch 0018:03EB:2136.0001: ... [ATML3432:00 03EB:2136] on

After "on " should read physical device name but it is left empty by the
driver.

Make it look better and fill in the physical device name.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Acked-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Reviewed-by: Daniel Martin <consume.noise@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>