msm: isp: fix for potentitial array out of bound access

There is no bound check on dual_hw_ms_cmd->num_src,
which is coming from userspace
num_src is used as the index for the input_src array
which has a size of 5.
The current code did not check the num_src to make sure
that it never exceeds the input_src array size.

CRs-Fixed: 2006169
Change-Id: If5927e06e70cce4afb0ae9f2cdfec80f76f83771
Signed-off-by: Senthil Kumar Rajagopal <skrajago@codeaurora.org>