nhk8815: add support for relocation

This patch defines all the needed symbols in the header file
and removes the now-unused config.mk in board directory.
Changes to board C file as requested.

Signed-off-by: Alessandro Rubini <rubini@gnudd.com>
Signed-off-by: Alessandro Rubini <rubini@unipv.it>
Acked-by: Andrea Gallo <andrea.gallo@stericsson.com>