staging: unisys: visorbus: fix payload memory usage in controlvm channel

Previously if controlvm message payloads (indicated in controlvm message
via struct controlvm_message.hdr.payload_vm_offset) were contained within
the bounds of the channel memory, we would fail to process any controlvm
message that contained payload data.  Reason is, the request_mem_region()
would fail, because it overlapped the channel memory.  Since
request_mem_region() doesn't actually serve a functional purpose anyway,
this was simply removed.

Signed-off-by: Timothy Sell <timothy.sell@unisys.com>
Signed-off-by: David Kershner <david.kershner@unisys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>