mac80211: add documentation and verbose variable names in

Add documentation and more verbose variable names to minstrel's
multi-rate-retry setup within function minstrel_get_rate() to
increase the readability of the algorithm.

Acked-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: Thomas Huehn <thomas@net.t-labs.tu-berlin.de>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

diff --cc net/mac80211/rc80211_minstrel.c
Simple merge

diff --cc net/mac80211/rc80211_minstrel.h
Simple merge