build: remove trailing whitespace from makefiles

Remove trailing whitespace from the makefiles, except for
trailing whitespace in the boilerplate comment headers.

Change-Id: Ib8ee87a51f00633ba15e1974ac0b311969bef1bf
Reviewed-on: http://gerrit.openafs.org/11456
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Reviewed-by: Chas Williams - CONTRACTOR <chas@cmf.nrl.navy.mil>
Reviewed-by: D Brashear <shadow@your-file-system.com>
Tested-by: D Brashear <shadow@your-file-system.com>