crypto: qcedev: change to use sg_init_one

Make change to init sg in qcedev functions which was
not initialized and was resulting in crashes with kernel
sg debug flag enabled; also fixed the sg buf vaddr issue
when sha request data is NULL.

Change-Id: I689f3a395ed0e07bc5aa0e83d043fb8251d0c203
Signed-off-by: Zhen Kong <zkong@codeaurora.org>