HID: fix oops in hid_check_keys_pressed()

If the device is not claimed by hid-input (i.e devices driver by userspace
hiddev/hidraw-based drivers, or completely detached from HID
and driver by libusb), we must not check the hid->inptus, as it
is not guaranteed to be initialized, as this is performed only for devices
handled by hid-input.

Reported-by: Guillaume Chazarain <guichaz@gmail.com>
Tested-by: Guillaume Chazarain <guichaz@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>