HID: nvidia-shield: add LEDS_CLASS dependency

The hid-nvidia-shield driver uses functions that are built
only when LEDS_CLASS is set, so make the driver depend on that
symbol to prevent build errors.

riscv32-linux-ld: drivers/hid/hid-nvidia-shield.o: in function `.L11':
hid-nvidia-shield.c:(.text+0x192): undefined reference to `led_classdev_unregister'
riscv32-linux-ld: drivers/hid/hid-nvidia-shield.o: in function `.L113':
hid-nvidia-shield.c:(.text+0xfa4): undefined reference to `led_classdev_register_ext'

Fixes: 09308562

 ("HID: nvidia-shield: Initial driver implementation with Thunderstrike support")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Rahul Rameshbabu <rrameshbabu@nvidia.com>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Cc: linux-input@vger.kernel.org
Reviewed-by: Rahul Rameshbabu <rrameshbabu@nvidia.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>