hyperv/hn: Add option to bind TX taskqueues to the specified CPU

[sepherosa_gmail.com]

Summary

It will be used to help tracking host side transmission ring selection issue; and will be turned on by default, once we have concrete result

[howard0su_gmail.com]

I worried so many options just brings headache to the end user without the clearly instruction on how to tune it. Please introduce new option when it is really needed. Maybe it is good time now to write a man page for hn.

[sepherosa_gmail.com]

In D5316#113452, @howard0su_gmail.com wrote:

I worried so many options just brings headache to the end user without the clearly instruction on how to tune it. Please introduce new option when it is really needed. Maybe it is good time now to write a man page for hn.

Well, I will complete the description: I _do_ need this to tracking the _host_ side transmission ring selection issue; and chances are high that I will set it by default in the end. If it's not necessary, I will not even bother to publish it.

As for the man page, yeah, we should have one; I probably will do it after the if_transmit work.