hyperv/vmbus: Alloc/Free monitor param in vmbus channel alloc/free.

Sponsored by:   Microsoft OSTC
Differential Revision:  https://reviews.freebsd.org/D7101

hyperv/vmbus: Move device register and channel free to the caller.

This paves the way for more cleanup/disentangle.

Sponsored by:   Microsoft OSTC
Differential Revision:  https://reviews.freebsd.org/D7102

hyperv/vmbus: Move new channel scan notification to device register

And nuke now unnecessary function indirection.

Sponsored by:   Microsoft OSTC
Differential Revision:  https://reviews.freebsd.org/D7103

hyperv/vmbus: Cleanup vmbus_chan_msgproc_choffer

Sponsored by:   Microsoft OSTC
Differential Revision:  https://reviews.freebsd.org/D7104

hyperv/vmbus: Nuke the channel open state.

Channel is either opened or not-opened.

Sponsored by:   Microsoft OSTC
Differential Revision:  https://reviews.freebsd.org/D7105

hyperv/vmbus: Cleanup vmbus_chan_add()

Sponsored by:   Microsoft OSTC
Differential Revision:  https://reviews.freebsd.org/D7106

hyperv/vmbus: Use sub-channel index to detect primary channel

In case that VMBUS_CHAN_ISPRIMARY is needed in the early place of
channel setup.

Sponsored by:   Microsoft OSTC
Differential Revision:  https://reviews.freebsd.org/D7108

hyperv/vmbus: Only add primary channels to vmbus channel list

- Make the vmbus_chan_add more straightforward.
- Partially fix the hv_vmbus_release_unattached_channels().

Sponsored by:   Microsoft OSTC
Differential Revision:  https://reviews.freebsd.org/D7109