Add new config to use multiple windows

Add the following configs in consideration with using multiple
windows for video rendering as overlay. They are used in calculation
of FIMD reserved memory.
- FB_S3C_NUM_OVLY_WIN : the number of overlay windows for video
rendering
- FB_S3C_NUM_BUF_OVLY_WIN : the number of framebuffers for overlay
windows




Change-Id: Id37b426a555d8742b9156fce0c398c10a68cd350
Signed-off-by: jung-min.oh <jung-min.oh@samsung.com>