image: android: Add routine to get dtbo params

Android Boot Image v1 adds "Recovery DTB" field in image header and
associate payload in boot image itself [1]. Payload should be in
Android DTB/DTBO format [2]. That "Recovery DTB" area should be only
populated for non-A/B devices, and only in recovery image.

Add function to get an address and size of that payload. That function
can be further used e.g. in 'abootimg' command to provide the user a way
to get the address of recovery dtbo from U-Boot shell, which can be
further parsed using 'adtimg' command.

[1] https://source.android.com/devices/bootloader/boot-image-header
[2] https://source.android.com/devices/architecture/dto/partitions



Signed-off-by: Sam Protsenko <joe.skb7@gmail.com>
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>