board: ti: am62x_evm: Add android bootflow

TODO: add build documentation to board doc

Add android boot flow support for AM62X board based on misc partition
to detect reboot reason and boot.img version 4 from android build
system.

Also add device tree overlay support for Android to enable CSI camera,
LVDS screen, HDMI Audio output.

This assumes that the `adtb_idx` env variable is a space-separated
list of indices.

Example:

Signed-off-by: Guillaume La Roque <glaroque@baylibre.com>
Co-developed-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>
Signed-off-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>