wifi: nl80211: fix puncturing bitmap policy

This was meant to be a u32, and while applying the patch
I tried to use policy validation for it. However, not only
did I copy/paste it to u8 instead of u32, but also used
the policy range erroneously. Fix both of these issues.

Fixes: d7c1a9a0

 ("wifi: nl80211: validate and configure puncturing bitmap")
Signed-off-by: Johannes Berg <johannes.berg@intel.com>