hyperv: fix apparent cut-n-paste error in send path teardown

c25aaf81: "hyperv: Enable sendbuf mechanism on the send path" added
some teardown code that looks like it was copied from the recieve path
above, but missed a variable name replacement.

Signed-off-by: Dave Jones <davej@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>