uboot-envtools: ath79: fix missing etactica eg200 support

Was inadvertantly missed from the inital forward port from ar71xx to
ath79.

Fixes: 1588114cf2 ("ath79: add etactica-eg200 support")
Signed-off-by: Karl Palsson <karlp@etactica.com>
[commit description/subject facelift]
Signed-off-by: Petr Štetiar <ynezz@true.cz>

package/boot/uboot-envtools/files/ath79

@@ -16,6 +16,7 @@ case "$board" in
 alfa-network,ap121f|\
 buffalo,bhr-4grv2|\
 engenius,ecb1750|\
+etactica,eg200|\
 glinet,gl-ar300m-lite|\
 glinet,gl-ar300m-nand|\
 glinet,gl-ar300m-nor|\