msm: vidc: Remove unnecessary checks in set property

Set property payload can be NULL in cases like requesting
I-Frame. Hence, erroring out if this payload is NULL is
not correct. Instead add a NULL check before memcopy of
payload.

CRs-Fixed: 2368458
Change-Id: Ia7ec9c20affd232109104147c450d293941c79b9
Signed-off-by: Vaibhav Deshu Venkatesh <vdeshuve@codeaurora.org>