[Change mt76 firmware to maintain in linux-mt76]

[Description]
Change mt76 firmware to maintain in linux-mt76
1. remove linux-firmware-mt76 package
2. add linux-mt76/files/src/firmware (from OpenWRT)
3. add descrition in mt76 bb to install firmware

[Release-log]
N/A

19 files changed
tree: 42297377ce823831fefe601f0060c80f5f105346
  1. classes/
  2. conf/
  3. recipes-connectivity/
  4. recipes-kernel/