mediatek: GL-MT6000: Add missing LED state definitions

mediatek: GL-MT6000: Add missing LED state definitions

Adjust LED names and provide the OpenWrt status indicator aliases
to actually use LEDs by the OpenWrt boot & sysupgrade processes.

* Name both LEDs clearly by the color
* Add the missing OpenWrt LED status indicator aliases and
  remove the now unnecessary default status from blue LED

After this commit, the LEDs are used as:

* bootloader, really early Linux boot: blue LED is on
* preinit/failsafe: white LED blinks rapidly
* late boot: white LED blinks slowly
* boot completed, running normally: blue LED is on

* sysupgrade: white LED blinks

Signed-off-by: Hannu Nyman <hannu.nyman@iki.fi>
(cherry picked from commit 5a82bb909bf16786b85508d2e974ddf0a14bb10c)