msm: vidc: Check for max secure instances allowed

Since secure flag is updated later, this change adds an additional check
for max instances allowed during set control call for setting secure flag

Change-Id: Idb48eeba661a5d294e4344aa758dc2ea4097d627
Signed-off-by: Akshay Chandrashekhar Kalghatgi <akalghat@codeaurora.org>