USB: usblcd: Push down BKL into driver

I'm pretty sure this can be eliminated however I couldn't prove (or find)
what stopped the device vanishing mid IOCTL_GET_HARD_VERSION. Perhaps a
USB wizard could double check that and see if the lock_kernel can go
entirely.

Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>