libcamera: Enabled camera overlays define based

Added imx219.dtbo file in the overlays, and added dtoverlay in
/boot/config.txt define based.

To enable Sony Raspberry pi camera imx219 sensor, need to set
the variable RASPBERRYPI_CAMERA_V2 as 1.

In future, we can add any camera overlays here to support and
use them with libcamera.

Signed-off-by: Madhavan Krishnan <madhavan.krishnan@linaro.org>
(cherry picked from commit b70c7b9021)
Signed-off-by: Ricardo Salveti <ricardo@foundries.io>

docs/extra-build-config.md

@@ -326,3 +326,17 @@ option:
         # Raspberry Pi 7\" display/touch screen \n \
         lcd_rotate=2 \n \
         '
+## Enable Raspberrypi Camera V2
+
+RaspberryPi does not have the unicam device ( RaspberryPi Camera ) enabled by default.
+Because this unicam device ( bcm2835-unicam ) as of now is used by libcamera opensource.
+So we have to explicitly set in local.conf.
+
+    RASPBERRYPI_CAMERA_V2 = "1"
+
+This will add the device tree overlays imx219 ( RaspberryPi Camera sensor V2 driver ) to config.txt.
+Also, this will enable adding Contiguous Memory Allocation value in the cmdline.txt.
+
+Ref.:
+* <https://github.com/raspberrypi/documentation/blob/master/linux/software/libcamera/README.md>
+* <https://www.raspberrypi.org/blog/an-open-source-camera-stack-for-raspberry-pi-using-libcamera/>