[arch-dev-public] [signoff] iwlwifi-3945-ucode 15.28.1.6-1

Updated the ucode for both architectures. I also removed the old ucode that didn't have the ABI version number in the filename, as that is only needed by very very very old versions of iwlwifi which probably fail to work anyway. Tested and working fine here on x86_64, please sign off.