cfg80211: use enum nl80211_dfs_regions for dfs_region everywhere

u8 was used in some other places, just stick to the enum,
this forces us to express the values that are expected.

Signed-off-by: Luis R. Rodriguez <mcgrof@do-not-panic.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

diff --cc include/net/regulatory.h
Simple merge

diff --cc net/wireless/nl80211.c
Simple merge

diff --cc net/wireless/reg.c
Simple merge

diff --cc net/wireless/reg.h
Simple merge