nl80211: Fix checkpatch warnings about blank lines

This patch fixes the following checkpatch.pl issues -
- Please don't use multiple blank lines
- Blank lines aren't necessary before a close brace
- Missing a blank line after declarations

Reviewed-by: Julian Calaby <julian.calaby@gmail.com>
Signed-off-by: Kirtika Ruchandani <kirtika.ruchandani@gmail.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>