Rename "short/long" retry counter to "data/rts" retry counter. The

Rename "short/long" retry counter to "data/rts" retry counter.  The
original names are inherited from ath(4)'s rate control algorithms,
while ath(4) actually uses short retry counter as rts retry counter,
and long retry counter as data retry counter.  According to the short
retry counter usage in 802.11 standard, it can be used as data retry
counter too.  Using the "short/long" retry counter is confusing (yah,
I was confused) and most hardwares seem to provide "data/rts" retry
counter, so switch to the new name: "data/rts" retry counter.

This change does not affect ONOE/AMRR TX rate control algorithms
operation in netproto/802_11, but it paves the way for Sample TX rate
control algorithm.