crypto: msm: check NULL pointer in _qcrypto_setkey_des()

add NULL pointer check before des_ekey()

Change-Id: I57c40b82fc5141c1666c3fd493b43e962f0d1ae9
Signed-off-by: Zhen Kong <zkong@codeaurora.org>
Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>
merge https://github.com/franciscofranco/hammerhead.git drivers : crypto