revert added hardware

it doesnt goes so :-)
.config:4:warning: override: TARGET_ar71xx_generic_TLMR3420 changes choice state
.config:5:warning: override: TARGET_ar71xx_generic_TLWR1043 changes choice state
.config:6:warning: override: TARGET_ar71xx_generic_TLWR941 changes choice state
.config:7:warning: override: TARGET_ar71xx_generic_TLWR842 changes choice state