Staging: hv: mousevsc: Get rid of mousevsc_on_send_completion()

We don't need to handle the "send complete" callback - nothing needs to be done
here; get rid of the code.

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