TKC1800: Correct error on LED backlight support (qmk#3408)

* Turn backlight support on by default

* Correct error on LED backlight support

Turns out, it doesn't work if you don't enable it in rules.mk. Who knew?

keyboards/tkc1800/rules.mk

@@ -60,7 +60,7 @@ COMMAND_ENABLE ?= yes        # Commands for debug and configuration
 SLEEP_LED_ENABLE ?= no       # Breathing sleep LED during USB suspend
 # if this doesn't work, see here: https://github.com/tmk/tmk_keyboard/wiki/FAQ#nkro-doesnt-work
 NKRO_ENABLE ?= yes           # USB Nkey Rollover
-BACKLIGHT_ENABLE ?= no       # Enable keyboard backlight functionality on B7 by default
+BACKLIGHT_ENABLE ?= yes       # Enable keyboard backlight functionality on B7 by default
 RGBLIGHT_ENABLE ?= yes       # Enable WS2812 RGB underlight. Do not enable this with audio at the same time.
 MIDI_ENABLE ?= no            # MIDI controls
 UNICODE_ENABLE ?= no         # Unicode