drm: enable DRM_MODE_FB_SECURE in drm framebuffer create

Enable checking for for DRM_MODE_FB_SECURE as valid flag
in frame buffer create routine.

CRs-Fixed: 2009714
Change-Id: Ia6ed81f38afbf925dca529f7a1d588f4d6c8b2fe
Signed-off-by: Alan Kwong <akwong@codeaurora.org>