netvsc_init() doesn't do anything relly meaningful, so we can simply remove
it. We can also remove the bogus SYSINIT (..., SI_SUB_KTHREAD_IDLE, ...),
which happens before vmbus_init() of SYSINIT(...,SI_SUB_SMP + 1,...), so it
can't do anything good.

Signed-off-by: Dexuan Cui <decui@microsoft.com>