leds: move the LED register dump to BANK3 and behind a command

leds_dump() printed the pin mux, the LED enables and every LED set on each
boot, from BANK2. It now lives in its own file in BANK3, where there is
room, and runs only on the new "leds" command, next to gpio and sds, so it
stays at hand for bringing up a new board without costing BANK2 or boot
output.

rtlplayground.c

@@ -1752,8 +1752,6 @@ void main(void)
 	leds_setup();
 	machine_custom_init();
 
-	leds_dump();
-
 	set_sys_led_state(SYS_LED_SLOW);
 
 	if (machine_detected.isRTL8373)