i40e: don't allow reduction of channels below active FD rules

If a driver is unable to maintain all current user supplied settings
from ethtool (or other sources), it is not ok for a user request to
succeed and silently trample over previous configuration.

To that end, if you change the number of channels, it must not be
allowed to reduce the number of channels (queues) below the current
flow director filter rules targets. In this case, return -EINVAL when
a request to reduce the number of channels would do so. In addition
log a warning to the kernel buffer explaining why we failed, and report
the rules which prevent us from lowering the number of channels.

Change-ID: If41464d63d7aab11cedf09e4f3aa1a69e21ffd88
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>