Staging: hv: hv_mouse: use a real struct hid_descriptor

The data coming from the vmbus is really a hid descriptor, so use that
structure instead of having to mess around with a character array and
pointer fun.

Cc: Hank Janssen <hjanssen@microsoft.com>
Cc: K. Y. Srinivasan <kys@microsoft.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>