bus/vmbus: fix check for mmap failure
bus/vmbus: fix check for mmap failure

The code was testing the result of mmap incorrectly.
I.e the test that a local pointer is not MAP_FAILED would
always succeed and therefore hid any potential problems.

Fixes: 831dba47bd36 ("bus/vmbus: add Hyper-V virtual bus support")
Cc: stable@dpdk.org

Signed-off-by: Stephen Hemminger <6e2d829dccd9a999246d37fa28053b3b607441a0@microsoft.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk