mac80211: use firmware from linux-firmware git

Use the firmware from linux-firmware git where possible.

Update some firmware files in that process and check for missing firmware files for some modules.

 * update Ralink firmwares
 * update ath9k_htc firmware
 * add firmware for mwl8k
 * add more firmware files for libertas-sd and libertas-usb

SVN-Revision: 27252