Export V4L2 APIs to support early camera.

Export V4L2 APIs to support early camera.

To mmap camera videos to the spriteC plane(Intel i915), early camera
will bypass DRM_IOCTL to avoid drm_master conflicting issues, and
call drm APIs directly. Because drm APIs are for user space
framworks and applications, it is necessary to export them for early
camera module.
For the details of early camera feature, please check the wiki page:
https://wiki.tizen.org/wiki/Early_Camera

Change-Id: I955ca2c73e9c33c5987ac8f36c7c730545ce1333
Signed-off-by: Fang, Neo <neo.fang@intel.com>