msm: vidc: Add vidioc_default functionality

V4l2 framework will call vidioc_default function
for private ioctl commands. Video driver needs
this function implementation to allow clients
to call private ioctl commands to video driver.

Change-Id: I670f6e4b22e5dae7334bc7d5e179d26b2bf5740f
Signed-off-by: Maheshwar Ajja <majja@codeaurora.org>