Disable capture side compose selections for the encoder.
This fixes the following v4l2-compliance complaint:

		fail: v4l2-test-formats.cpp(1662): IS_ENCODER(node)
	test Composing: FAIL
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>