Hi,
I found this code in u-boot\arch\powerpc\lib\board.c
#if defined(CONFIG_STATUS_LED) && defined(STATUS_LED_BOOT)
status_led_set(STATUS_LED_BOOT, STATUS_LED_BLINKING);
#endif
This seems to do what you want I don't see a flag used so that this will be executed only
for one processor, this code is used for the all processors from the PowerPC family. The
CONFIG_STATUS_LED flag is used to enable the blinking feature in particular.
Maybe this can be a starting point for you,
Catalin