Documentation: hyperv: Update VMBus doc with new features and info

Starting in the 6.15 kernel, VMBus interrupts are automatically
assigned away from a CPU that is being taken offline. Add documentation
describing this case.

Also add details of Hyper-V behavior when the primary channel of
a VMBus device is closed as the result of unbinding the device's
driver. This behavior has not changed, but it was not previously
documented.

Signed-off-by: Michael Kelley <mhklinux@outlook.com>
Link: https://lore.kernel.org/r/20250520044435.7734-1-mhklinux@outlook.com


Signed-off-by: Wei Liu <wei.liu@kernel.org>
Message-ID: <20250520044435.7734-1-mhklinux@outlook.com>