[media] omap: Fix Kconfig dependencies on OMAP2

Resolves the following warning that appears with allmodconfig on -arm:
	warning: (VIDEO_OMAP2_VOUT && DRM_OMAP) selects OMAP2_DSS which has unmet direct dependencies (HAS_IOMEM && ARCH_OMAP2PLUS)
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/platform/omap/Kconfig

@@ -6,7 +6,7 @@ config VIDEO_OMAP2_VOUT
 	depends on ARCH_OMAP2 || ARCH_OMAP3
 	select VIDEOBUF_GEN
 	select VIDEOBUF_DMA_CONTIG
-	select OMAP2_DSS
+	select OMAP2_DSS if HAS_IOMEM && ARCH_OMAP2PLUS
 	select OMAP2_VRFB if ARCH_OMAP2 || ARCH_OMAP3
 	select VIDEO_OMAP2_VOUT_VRFB if VIDEO_OMAP2_VOUT && OMAP2_VRFB
 	default n