mac80211: Modify mesh_set_ht_prot_mode() to have less identation

Determining types of peers is modified to have less indentation. This change is
suggested by Johannes. This patch also corrects the reference in comment to
IEEE 802.11-2012 version.

Signed-off-by: Ashok Nagarajan <ashok@cozybit.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>