[media] v4l: omap4iss: tighten omap4iss dependencies

The OMAP4 camera support depends on I2C and VIDEO_V4L2, both
of which can be loadable modules. This causes build failures
if we want the camera driver to be built-in.

This can be solved by turning the option into "tristate",
which unfortunately causes another problem, because the
driver incorrectly calls a platform-internal interface
for omap4_ctrl_pad_readl/omap4_ctrl_pad_writel.

Instead, this patch just forbids the invalid configurations
and ensures that the driver can only be built if all its
dependencies are built-in.

Cc: stable@vger.kernel.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

drivers/staging/media/omap4iss/Kconfig

 config VIDEO_OMAP4
 	bool "OMAP 4 Camera support"
-	depends on VIDEO_V4L2 && VIDEO_V4L2_SUBDEV_API && I2C && ARCH_OMAP4
+	depends on VIDEO_V4L2=y && VIDEO_V4L2_SUBDEV_API && I2C=y && ARCH_OMAP4
 	select VIDEOBUF2_DMA_CONTIG
 	---help---
 	  Driver for an OMAP 4 ISS controller.