amdkfd: fix spelling mistake in kfd_ioctl_dbg_unrgesiter

Trivial fix to spelling mistake, rename kfd_ioctl_dbg_unrgesiter
to kfd_ioctl_dbg_unregister

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Oded Gabbay <oded.gabbay@gmail.com>