hyperv: Add missing field to hv_output_map_device_interrupt

hyperv: Add missing field to hv_output_map_device_interrupt

[ Upstream commit 4cd661c248b6671914ad59e16760bb6d908dfc61 ]

This field is unused, but the correct structure size is needed
when computing the amount of space for the output argument to
reside, so that it does not cross a page boundary.

Signed-off-by: Nuno Das Neves <nunodasneves@linux.microsoft.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>