this patch addes exynos_drm_gem_init() creating and initialzing a gem.
allocation functions could use this function to create new gem and
it changes size type of exynos_drm_gem_create structure to 64bit
and also corrects comments to exynos_drm_gem_create structure.
Signed-off-by: NInki Dae <inki.dae@samsung.com>
Signed-off-by: NKyungmin Park <kyungmin.park@samsung.com>