mt8183: config: add load_recoveryimg function

/recovery is a standard Android partition used for applying updates
or erasing userdata[1]

Load RecoveryOS from the recovery partition and allow to bootm after.

[1] https://source.android.com/devices/tech/ota/nonab

Signed-off-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>