drm: renesas: shmobile: Atomic conversion part 1

Implement atomic mode setting for both the primary and overlay planes.
This involves:
- Moving the primary plane handling code from CRTC mode setting to
plane handling shared by primary and overlay planes,
- Adding basic CRTC and mode config atomic mode setting ops, which
don't do much yet.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/a6b698a1c8c1eaf631c2f928f5888ab5fe7aa4c3.1694767209.git.geert+renesas@glider.be

drm: renesas: shmobile: Unify plane allocation

Unify primary and overlay plane allocation:
- Enhance shmob_drm_plane_create() so it can be used to create the
primary plane, too,
- Move overlay plane creation next to primary plane creation.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/adbc5febc0099fd1910f32a7af1c8e0f570f74b4.1694767209.git.geert+renesas@glider.be

drm: Place Renesas drivers in a separate dir

Create vendor specific renesas directory and move renesas drivers
to that directory.

Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Acked-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>