Staging: hv: remove hv_mouse driver as it's now in the hid directory

This removes the hv_mouse driver as it's now in Jiri's HID tree in the
"proper" place.

Cc: KY Srinivasan <kys@microsoft.com>
Cc: Jiri Kosina <jikos@jikos.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>