bus/vmbus: fix race in subchannel creation

bus/vmbus: fix race in subchannel creation

When using multiple queues, there was a race with the kernel
in setting up the second channel. This regression is due to a kernel change
which does not allow accessing sysfs files for Hyper-V channels that are not opened.

The fix is simple, just move the logic to detect not ready
sub channels earlier in the existing loop.

Fixes: 831dba47bd36 ("bus/vmbus: add Hyper-V virtual bus support")
Cc: stable@dpdk.org
Reported-by: Mohammed Gamal <mgamal@redhat.com>
Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>