Makefile: add Lantiq NAND SPL images

Signed-off-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
WIP: tools: lantiq: add NAND SPL support

Signed-off-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
WIP: MIPS: lantiq: add NAND SPL support

Signed-off-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
WIP: MIPS: vrx200: add NAND SPL support

Signed-off-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
MIPS: lantiq: easy80920: add NAND SPL support

Signed-off-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
MIPS: lantiq: easy80920: enable SPL debug

Signed-off-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>