[media] s5p_cec: set the CEC_CAP_NEEDS_HPD flag if needed

Use the needs-hpd DT property to determine if the CEC_CAP_NEEDS_HPD
should be set.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>