[media] v4l2: Fix the possible memory leak in v4l2 framework

If the size of the command passed to video_usercopy function
is bigger than the supported stack size, the required size
is allocated from heap. In this case, the memory needs to
be freed, otherwise can result in memory leak

CRs-Fixed: 547486
Change-Id: I5268673cf5941ae55620592fadacbabee36cdf29
Signed-off-by: Lakshmi Narayana Kalavala <lkalaval@codeaurora.org>