linux-firmware: update hash of LICENSE.amdgpu

In commit 51435be1 ("linux-firmware:
bump version to latest 8d69bab"), the hash of the LICENSE.amdgpu was
not updated as it should have been. Indeed, there was a copyright year
change in this file:

-Copyright (C) 2017  Advanced Micro Devices, Inc. All rights reserved.
+Copyright (C) 2018  Advanced Micro Devices, Inc. All rights reserved.

which changed the hash of this license file.

Fixes:

  http://autobuild.buildroot.net/results/cc0e44fa854597b8a83dfdcd6435cb55af1c8571/



Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>