comerr: Don't cast returns from malloc()

comerr: Don't cast returns from malloc()

malloc() returns a (void *) on all of our current platforms. So,
don't bother casting the return value before assigning it - it is
unnecessary noise.

Change-Id: Idc5f098a20809a5f869c4ea9f3970e598520c0e9
Reviewed-on: http://gerrit.openafs.org/7468
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementix.org>