wbgen-regs/wr-dio-regs.wb and .h: from wr-nic ohwr project

The wb file is copied from modules/wrsw_dio/wrsw_dio.wb,
commit f00d7ff (branch jdiaz at time of this commit). The .h
is built by "make wr-dio-regs.h" in this directory.
Signed-off-by: Alessandro Rubini <rubini@gnudd.com>