HID: core: store the unique system identifier in hid_device

[ Upstream commit 1e839143

 ]

This unique identifier is currently used only for ensuring uniqueness in
sysfs. However, this could be handful for userspace to refer to a specific
hid_device by this id.

2 use cases are in my mind: LEDs (and their naming convention), and
HID-BPF.

Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Link: https://lore.kernel.org/r/20220902132938.2409206-9-benjamin.tissoires@redhat.com
Stable-dep-of: fc43e9c8

 ("HID: fix HID device resource race between HID core and debugging support")
Signed-off-by: Sasha Levin <sashal@kernel.org>