remove bootargs from dts

target/linux/ramips/dts/3G-6200N.dts

target/linux/ramips/dts/3G-6200NL.dts

target/linux/ramips/dts/3G300M.dts

target/linux/ramips/dts/AIR3GII.dts

target/linux/ramips/dts/ALL0239-3G.dts

target/linux/ramips/dts/ALL0256N-4M.dts

target/linux/ramips/dts/ALL0256N-8M.dts

target/linux/ramips/dts/ALL5002.dts

target/linux/ramips/dts/ARGUS_ATP52B.dts

target/linux/ramips/dts/BC2.dts

target/linux/ramips/dts/BR-6425.dts

target/linux/ramips/dts/BROADWAY.dts

target/linux/ramips/dts/CARAMBOLA.dts

target/linux/ramips/dts/D105.dts

target/linux/ramips/dts/DAP-1350.dts

target/linux/ramips/dts/DIR-300-B1.dts

target/linux/ramips/dts/DIR-600-B1.dts

target/linux/ramips/dts/DIR-600-B2.dts

target/linux/ramips/dts/DIR-615-D.dts

target/linux/ramips/dts/DIR-615-H1.dts