rx: Don't cast returns from allocator

rx: Don't cast returns from allocator

malloc() and osi_Alloc both return (void *). So, don't bother
casting the return value before assigning it - its unnecessary
noise.

Change-Id: I71a66a8fa0d9f49f4833dd77bbb55422e6f20d6f
Reviewed-on: http://gerrit.openafs.org/7466
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementix.org>