Don't cast the return from realloc()

Don't cast the return from realloc()

realloc takes, and returns a (void *) argument. So we don't need to
cast these parameters into, or out of, realloc. Doing so is just
noise, so don't bother.

Change-Id: I64e721703536515b2e315e3b033eb2be14f7e18c
Reviewed-on: http://gerrit.openafs.org/7455
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementix.org>