drm: shmobile: Make DRM_SHMOBILE visible on Renesas SoC platforms

The LCD Controller supported by the drm-shmob driver is present
on SuperH SH-Mobile SoCs, and on Renesas ARM SH/R-Mobile SoCs.
Unfortunately its config option is not visible on either, so the user
can never enable the support.

Fix this by dropping the dependency on ARM (for SuperH), and by widening
the dependency range to ARCH_RENESAS (for ARM).

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/40ac67e0887d833ab4a3f1ec24828dedf0d8e108.1684854992.git.geert+renesas@glider.be