regulatory: allow VHT channels in world roaming

For VHT, the wider bandwidths (up to 160 MHz) need
to be allowed. Since world roaming only covers the
case of connecting to an AP, it can be opened up
there, we will rely on the AP to know the local
regulations.

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