This commit: 1. Renames beeline-trx recipe in mt7621.mk to arcadyan-trx. The recipe is necessary for: - MTS WG430223 (Arcadyan WG430223) - Beeline Smartbox Flash (Arcadyan WG443223) 2. Allows specify custom trx magic which is different for the routers mentined above. Signed-off-by: Mikhail Zhilkin <csharper2005@gmail.com>