Drivers: hv: vmbus: Remove unused extern declaration vmbus_ontimer()

Since commit 30fbee49

 ("Staging: hv: vmbus: Get rid of the unused function vmbus_ontimer()")
this is not used anymore, so can remove it.

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Link: https://lore.kernel.org/r/20230725142108.27280-1-yuehaibing@huawei.com


Signed-off-by: Wei Liu <wei.liu@kernel.org>