- Add ral(4) for Ralink RT2500/RT2501/RT2600 chip based wireless NIC

- Add ral(4) for Ralink RT2500/RT2501/RT2600 chip based wireless NIC
- Add ral(4) to GENERIC and LINT
- Add man page for ral(4)
  Reviewed-by: swildner
Thank Damien Bergamini for his work on this driver

For RT2500:
- Fix a ieee80211_node leakage
- Due to the inter-dependency nature of DONE/(ENCRYPT|DECRYPT) intr, reap desc
  rings twice if one of them comes.  This change gives me ~17.6% TX performance
  boost on my ASUS WL-107G (WPA is used here):
  Original way of TX/RX intr processing
  ------------------------------------------------------------
  Client connecting to sephe-test, TCP port 5001
  TCP window size: 32.5 KByte (default)
  ------------------------------------------------------------
  [  3] local 192.168.2.14 port 1063 connected with 192.168.2.254 port 5001
  [  3]  0.0- 5.0 sec  10.2 MBytes  17.1 Mbits/sec
  [  3]  5.0-10.0 sec  9.95 MBytes  16.7 Mbits/sec
  [  3] 10.0-15.0 sec  9.67 MBytes  16.2 Mbits/sec
  [  3] 15.0-20.0 sec  10.1 MBytes  17.0 Mbits/sec
  [  3] 20.0-25.0 sec  10.2 MBytes  17.1 Mbits/sec
  [  3] 25.0-30.0 sec  10.0 MBytes  16.8 Mbits/sec
  [  3] 30.0-35.0 sec  9.91 MBytes  16.6 Mbits/sec
  [  3] 35.0-40.0 sec  10.3 MBytes  17.2 Mbits/sec
  [  3] 40.0-45.0 sec  9.87 MBytes  16.6 Mbits/sec
  [  3] 45.0-50.0 sec  9.94 MBytes  16.7 Mbits/sec
  [  3] 50.0-55.0 sec  10.2 MBytes  17.2 Mbits/sec
  [  3] 55.0-60.0 sec  9.73 MBytes  16.3 Mbits/sec
  [  3]  0.0-60.0 sec    120 MBytes  16.8 Mbits/sec

  Adapted way of TX/RX intr processing
  ------------------------------------------------------------
  Client connecting to sephe-test, TCP port 5001
  TCP window size: 32.5 KByte (default)
  ------------------------------------------------------------
  [  3] local 192.168.2.14 port 1062 connected with 192.168.2.254 port 5001
  [  3]  0.0- 5.0 sec  11.8 MBytes  19.8 Mbits/sec
  [  3]  5.0-10.0 sec  11.5 MBytes  19.4 Mbits/sec
  [  3] 10.0-15.0 sec  11.1 MBytes  18.7 Mbits/sec
  [  3] 15.0-20.0 sec  12.0 MBytes  20.1 Mbits/sec
  [  3] 20.0-25.0 sec  12.6 MBytes  21.2 Mbits/sec
  [  3] 25.0-30.0 sec  11.7 MBytes  19.6 Mbits/sec
  [  3] 30.0-35.0 sec  12.3 MBytes  20.7 Mbits/sec
  [  3] 35.0-40.0 sec  11.9 MBytes  19.9 Mbits/sec
  [  3] 40.0-45.0 sec  11.9 MBytes  19.9 Mbits/sec
  [  3] 45.0-50.0 sec  12.2 MBytes  20.4 Mbits/sec
  [  3] 50.0-55.0 sec  12.1 MBytes  20.2 Mbits/sec
  [  3] 55.0-60.0 sec  12.3 MBytes  20.7 Mbits/sec
  [  3]  0.0-60.0 sec    143 MBytes  20.0 Mbits/sec

Obtained-from: FreeBSD