staging: hv: Fixed the value of the 64bit-hole inside ring buffer

Fixed the value of the 64bit-hole inside ring buffer, this
caused a problem on Hyper-V when running checked Windows builds.

Checked builds of Windows are used internally and given to external
system integrators at times. They are builds that for example that all
elements in a structure follow the definition of that Structure. The bug
this fixed was for a field that we did not fill in at all (Because we do
Not use it on the Linux side), and the checked build of windows gives
errors on it internally to the Windows logs.

This fixes that error.

Signed-off-by: Hank Janssen <hjanssen@microsoft.com>
Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>