hv_netvsc: fix netvsc_send_completion to avoid multiple message length checks

The switch statement in netvsc_send_completion() is incorrectly validating
the length of incoming network packets by falling through to the next case.
Avoid the fallthrough. Instead break after a case match and then process
the complete() call.
The current code has not caused any known failures. But nonetheless, the
code should be corrected as a different ordering of the switch cases might
cause a length check to fail when it should not.

Signed-off-by: Sonia Sharma <sonia.sharma@linux.microsoft.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>