[media] media: davinci: remove unneeded dependency ARCH_OMAP3

this patch removes unneeded dependency of ARCH_OMAP3
on VIDEO_DM6446_CCDC.
Also the top level platform Makefile descended into
davinci/ without any dependency so just drop the
dependency obj-y, as obj-$(CONFIG_ARCH_DAVINCI)
already exists.

Reported-by: Andreas Ruprecht <rupran@einserver.de>
Signed-off-by: Lad, Prabhakar <prabhakar.csengg@gmail.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>