linux-firmware: update Atheros firmware license

This makes the license Operating System agnostic and updates
the patent license grant for use of the firmware license specifically
on the Atheros chipsets.

This allows us to share the same license between all Atheros chipsets,
ath9k, ath9k_htc, ath6kl, and future chipsets.

Cc: ath9k-devel@atheros.com
Cc: Len Widra <len.widra@atheros.com>
Cc: Brian Lee <briank.lee@atheros.com>
Cc: Adam Tachner <atachner@atheros.com>
Cc: Paul Lever <Paul.Lever@atheros.com>
Cc: Vipin Mehta <vipin.mehta@atheros.com>
Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>