drm/vkms: Add basic CRTC initialization

This commit adds the essential infrastructure for around CRTCs which
is composed of: a new data struct for output data information, a
function for creating planes, and a simple encoder attached to the
connector. Finally, due to the introduction of a new initialization
function, connectors were moved from vkms_drv.c to vkms_display.c.

Signed-off-by: Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com>
Reviewed-by: Haneen Mohammed <hamohammed.sa@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/b6e27bc6a54f5cb340658fa5969f7b48fbfbf1b7.1526514457.git.rodrigosiqueiramelo@gmail.com