uboot-envtools: add support for GL.iNet GL-AR750

Signed-off-by: Piotr Dymacz <[email protected]>

package/boot/uboot-envtools/files/ar71xx

@@ -31,6 +31,7 @@ cr5000|\
 eap300v2|\
 ens202ext|\
 gl-ar300m|\
+gl-ar750|\
 hornet-ub|\
 hornet-ub-x2|\
 jwap230|\