msm-shared: scm: Properly init SCM command struct on alloc

Init SCM command struct fields (including response and buffers) to zero
on SCM command allocation. This fixes possible error on restore_secure_cfg()
call when the SCM command response buffer is not zero - it appears the
response value is not set which is interpreted as error when it is not zero
by default

CRs-Fixed: 596993

Change-Id: Ia0e80918765ae8db93c9a126cda640e6352cba42
1 file changed