net/hyperv: Use the built-in macro KBUILD_MODNAME for this driver

Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Cc: Olaf Hering <olaf@aepfle.de>
Signed-off-by: David S. Miller <davem@davemloft.net>