linux-firmware: Removed codeversion from brcm firmware filenames.

The basename-apiversion-codeversion construction for firmware filenames is not
used by most other firmware files, adds complexity, and is not providing any
value.  Renamed the firmware files using just basename-apiversion and fixed
WHENCE to have correct names and path to these files.

Signed-off-by: Henry Ptasinski <henryp@broadcom.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>