[media] stm32-dcmi: STM32 DCMI camera interface driver

This V4L2 subdev driver enables Digital Camera Memory Interface (DCMI)
of STMicroelectronics STM32 SoC series.

Signed-off-by: Yannick Fertre <yannick.fertre@st.com>
Signed-off-by: Hugues Fruchet <hugues.fruchet@st.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>