staging: sst: remove the kernel locking in ioctl

kernel locking in ioctl was introduced when ioctl function was
moved from ioctl to unlocked ioctl
This is no longer required hence removed

Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>