Staging: slicoss: Fix smatch warning in slicoss.c

This patch fixes following smatch warning:
slicoss/slicoss.c:1429 slic_cmdq_addcmdpage() error: we previously assumed 'pslic_handle' could be null

Signed-off-by: Monam Agarwal <monamagarwal123@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>