ramips: rt305x: add support for the ZyXEL NBG-419N board

target/linux/ramips/base-files/etc/diag.sh

...ramips/base-files/etc/hotplug.d/firmware/10-rt2x00-eeprom

target/linux/ramips/base-files/lib/ramips.sh

target/linux/ramips/base-files/lib/upgrade/platform.sh

.../ramips/files/arch/mips/include/asm/mach-ralink/machine.h

target/linux/ramips/files/arch/mips/ralink/rt305x/Kconfig

target/linux/ramips/files/arch/mips/ralink/rt305x/Makefile

...inux/ramips/files/arch/mips/ralink/rt305x/mach-nbg-419n.c

target/linux/ramips/image/Makefile

target/linux/ramips/rt305x/config-2.6.39