spi_qsd: Verify pointers prior to redirection

Redirection on a NULL pointer leads to a system crash.
Here we verify pointers which potentially may be NULL
before a redirection.

Change-Id: I72b856e52f63b13e517c28d8dbb04e1f333f8065
Signed-off-by: Gilad Avidov <gavidov@codeaurora.org>