[media] fix compilation with both V4L2 and I2C as 'm'

When config options are:
	CONFIG_VIDEO_DEV=y
	CONFIG_VIDEO_V4L2=m
	CONFIG_I2C=m

Compilation breaks, as reported by:
	https://bugzilla.kernel.org/show_bug.cgi?id=55681

Before changeset 7b34be71,
no compilation errors occurred. However, the I2C code there at
v4l2-device was incorrectly disabled.
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/v4l2-core/Makefile

@@ -10,7 +10,7 @@ ifeq ($(CONFIG_COMPAT),y)
   videodev-objs += v4l2-compat-ioctl32.o
 endif
 
-obj-$(CONFIG_VIDEO_DEV) += videodev.o
+obj-$(CONFIG_VIDEO_V4L2) += videodev.o
 obj-$(CONFIG_VIDEO_V4L2_INT_DEVICE) += v4l2-int-device.o
 obj-$(CONFIG_VIDEO_V4L2) += v4l2-common.o