leds: move documentation to readme, broken on -M virt

kernel_config_fragment/default

@@ -130,52 +130,6 @@ CONFIG_UIO_PCI_GENERIC=m
 
 ## ARM
 
-# LEDs:
-#
-#     cd /sys/class/leds/versatile:0
-#     cat max_brightness
-#     echo 255 >brightness
-#
-# https://raspberrypi.stackexchange.com/questions/697/how-do-i-control-the-system-leds-using-my-software
-#
-# Relevant QEMU files:
-#
-# - hw/arm/versatilepb.c
-# - hw/misc/arm_sysctl.c
-#
-# Relevant kernel files:
-#
-# - arch/arm/boot/dts/versatile-pb.dts
-# - drivers/leds/led-class.c
-# - drivers/leds/leds-sysctl.c
-#
-# Try hacking QEMU's `hw/misc/arm_sysctl.c` with a printf:
-#
-#     static void arm_sysctl_write(void *opaque, hwaddr offset,
-#                                 uint64_t val, unsigned size)
-#     {
-#         arm_sysctl_state *s = (arm_sysctl_state *)opaque;
-#
-#         switch (offset) {
-#         case 0x08: /* LED */
-#             printf("LED val = %llx\n", (unsigned long long)val);
-#
-# to observe when the callback is made. But beware that one of the LEDs
-# has a heartbeat trigger by default (specified on dts), so it will produce a lot of output.
-#
-CONFIG_LEDS_CLASS=y
-CONFIG_LEDS_CLASS_FLASH=y
-CONFIG_LEDS_SYSCON=y
-CONFIG_LEDS_TRIGGERS=y
-CONFIG_LEDS_TRIGGER_BACKLIGHT=y
-CONFIG_LEDS_TRIGGER_CPU=y
-CONFIG_LEDS_TRIGGER_DEFAULT_ON=y
-CONFIG_LEDS_TRIGGER_GPIO=y
-CONFIG_LEDS_TRIGGER_HEARTBEAT=y
-CONFIG_LEDS_TRIGGER_ONESHOT=y
-CONFIG_LEDS_TRIGGER_TIMER=y
-CONFIG_NEW_LEDS=y
-
 # Like CONFIG_X86_PTDUMP for ARM.
 CONFIG_ARM64_PTDUMP=y
 

kernel_config_fragment/leds

@@ -0,0 +1,12 @@
+CONFIG_LEDS_CLASS=y
+CONFIG_LEDS_CLASS_FLASH=y
+CONFIG_LEDS_SYSCON=y
+CONFIG_LEDS_TRIGGERS=y
+CONFIG_LEDS_TRIGGER_BACKLIGHT=y
+CONFIG_LEDS_TRIGGER_CPU=y
+CONFIG_LEDS_TRIGGER_DEFAULT_ON=y
+CONFIG_LEDS_TRIGGER_GPIO=y
+CONFIG_LEDS_TRIGGER_HEARTBEAT=y
+CONFIG_LEDS_TRIGGER_ONESHOT=y
+CONFIG_LEDS_TRIGGER_TIMER=y
+CONFIG_NEW_LEDS=y