wireless: correct sparse warning in generated regdb.c

  CHECK   net/wireless/regdb.c
net/wireless/regdb.c:8:34: warning: symbol 'reg_regdb' was not declared.  Should it be static?
net/wireless/regdb.c:11:5: warning: symbol 'reg_regdb_size' was not declared. Should it be static?

Simply include the also generated regdb.h.

Signed-off-by: John W. Linville <linville@tuxdriver.com>