drm: renesas: shmobile: Rename shmob_drm_connector.connector

Rename the "connector" member of the shmob_drm_connector subclass
structure to "base", to improve readability.

Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Sui Jingfeng <suijingfeng@loongson.cn>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/2382c4c796b53b5d2b24f99b85954ce632f21b90.1694767209.git.geert+renesas@glider.be