remove redundant struct initialization

struct cipher_data *out (sess_new->cdata) is already initiallized to
zero as 'ses_new = kzalloc(...)' in the caller function
crypto_create_session

Signed-off-by: Cristian Stoica <cristian.stoica@freescale.com>
initialize struct memory to zero in a single call

kmalloc + memset(0) can be replaced with a single call to kzalloc for
the same results

Signed-off-by: Cristian Stoica <cristian.stoica@freescale.com>