[U-Boot] An anomaly in image booting code

In common/bootm.c there's a function do_bootm_states. Among other things this sets the global variable images->states to the supplied states. If those states include the flag BOOTM_START it then calls a function bootm_start, which then memset-s the whole of state to zero before setting the flag BOOTM_STATE_START.

This code has been there for a few years now, so it obviously doesn't break anything major - but what is it supposed to do?