BOARDIOC_SWITCH_BOOT is required to communicate the boot partition from
userspace (OTA subsystem) to board. It can be used to change the system
boot behavior. So it's useful for A/B boot or even single boot case.
For the board support A/B boot case:
1. Download the new image from the sever
2. Write the new image to the alternative partition
3. Call BOARDCTL_SWITCH_BOOT to the alternative system
For single boot partition case:
1. Download the new image from the sever
2. Call BOARDCTL_SWITCH_BOOT and reboot to a small system
3. Write the new image to the main partition in the small system
4. Call BOARDCTL_SWITCH_BOOT again to the main system
Change-Id: Ifebb495784ecf06842946a249bec64f75dce894f
Signed-off-by: liuhaitao <liuhaitao@xiaomi.com>
a02f450773