drivers: hv: Add a module description line to the hv_vmbus driver

This patch only adds a MODULE_DESCRIPTION statement to the driver.
This change is only cosmetic, so there should be no runtime impact.

Signed-off-by: Joseph Salisbury <joseph.salisbury@microsoft.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>