[media] v4l: omap4iss: Enable driver compilation as a module

Now that the driver doesn't use the non-exported omap4_ctrl_pad_readl
and omap4_ctrl_pad_writel functions nothing prevents it from being
compiled as a module anymore.
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

drivers/staging/media/omap4iss/Kconfig

 config VIDEO_OMAP4
-	bool "OMAP 4 Camera support"
+	tristate "OMAP 4 Camera support"
 	depends on VIDEO_V4L2=y && VIDEO_V4L2_SUBDEV_API && I2C=y && ARCH_OMAP4
 	depends on HAS_DMA
 	select MFD_SYSCON

drivers/staging/media/omap4iss/TODO

-* Make the driver compile as a module
 * Fix FIFO/buffer overflows and underflows
 * Replace dummy resizer code with a real implementation
 * Fix checkpatch errors and warnings