drm/rcar: stop using 'imply' for dependencies

The meaning of the 'imply' keyword has changed recently, and neither the
old meaning (select the symbol if its dependencies are met) nor the new
meaning (enable it by default, but let the user set any other setting)
is what we want here.

Work around this by adding two more Kconfig options that lead to
the correct behavior: if DRM_RCAR_USE_CMM and DRM_RCAR_USE_LVDS
are enabled, that portion of the driver becomes usable, and no
configuration results in a link error.

This avoids a link failure:

arm-linux-gnueabi-ld: drivers/gpu/drm/rcar-du/rcar_du_crtc.o: in function `rcar_du_crtc_atomic_begin':
rcar_du_crtc.c:(.text+0x1444): undefined reference to `rcar_cmm_setup'
arm-linux-gnueabi-ld: drivers/gpu/drm/rcar-du/rcar_du_crtc.o: in function `rcar_du_crtc_atomic_enable':
rcar_du_crtc.c:(.text+0x14d4): undefined reference to `rcar_cmm_enable'
arm-linux-gnueabi-ld: rcar_du_crtc.c:(.text+0x1548): undefined reference to `rcar_cmm_setup'
arm-linux-gnueabi-ld: drivers/gpu/drm/rcar-du/rcar_du_crtc.o: in function `rcar_du_crtc_atomic_disable':
rcar_du_crtc.c:(.text+0x18b8): undefined reference to `rcar_cmm_disable'
arm-linux-gnueabi-ld: drivers/gpu/drm/rcar-du/rcar_du_kms.o: in function `rcar_du_modeset_init':

Link: https://lore.kernel.org/all/20200417155553.675905-5-arnd@arndb.de/


Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>