HID: bigben: fix slab-out-of-bounds Write in bigben_probe

There is a slab-out-of-bounds Write bug in hid-bigbenff driver.
The problem is the driver assumes the device must have an input but
some malicious devices violate this assumption.

Fix this by checking hid_device's input is non-empty before its usage.

Reported-by: syzkaller <syzkaller@googlegroups.com>
Signed-off-by: Dongliang Mu <mudongliangabcd@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>