doc: fix sysfs ABI documentation

In 4.9 kernel, the sysfs files for Hyper-V VMBus changed name but
the documentation files were not updated. The current sysfs file
names are /sys/bus/vmbus/devices/<UUID>/...

See commit 9a56e5d6a0ba ("Drivers: hv: make VMBus bus ids persistent")
and commit f6b2db08 ("vmbus: make sysfs names consistent with PCI")

Reported-by: Michael Kelley <mikelley@microsoft.com>
Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Cc: stable@vger.kernel.org
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>