Revert "ar71xx: fix Archer C7 LED colour names"

This reverts commit e79ecb4c.

The commit was incomplete and the issue that should be fixed isn't
that easy fixable. The Archer C7 mach file is used for the Archer C5,
WDR4900 and WDR7500 as well. Where the WDRs in compare to the Archer
do have blue LEDs.

Signed-off-by: Mathias Kresin <dev@kresin.me>