crypto: msm: qcrypto: Fix null pointer dereference error in qcrypto driver

Validity of pointer returned from kmalloc is checked before
dereferencing it and the correct error code is propogated
forward for effective handling by the system.

Change-Id: If2fc0395f19b2cc07a3655571e52217d67a7ef93
Signed-off-by: Prerna Kalla <prernak@codeaurora.org>