[MIPS] Remove support for NEC DDB5074.

Documentation/feature-removal-schedule.txt

arch/mips/Kconfig

arch/mips/Makefile

arch/mips/configs/atlas_defconfig

arch/mips/configs/bigsur_defconfig

arch/mips/configs/capcella_defconfig

arch/mips/configs/cobalt_defconfig

arch/mips/configs/db1000_defconfig

arch/mips/configs/db1100_defconfig

arch/mips/configs/db1200_defconfig

arch/mips/configs/db1500_defconfig

arch/mips/configs/db1550_defconfig

arch/mips/configs/ddb5476_defconfig

arch/mips/configs/ddb5477_defconfig

arch/mips/configs/decstation_defconfig

arch/mips/configs/e55_defconfig

arch/mips/configs/ev64120_defconfig

arch/mips/configs/ev96100_defconfig

arch/mips/configs/ip22_defconfig

arch/mips/configs/ip27_defconfig