ena: Add configuration notifications interface support

This commit is part of the effort of notifying the user of non-optimal
or performance impacting practices.
A new interface is serving as a communication channel
between the device and the driver. One of the goals of this channel is
to create a new mechanism of notifying the driver and user in case of
sub-optimal configuration using a bitmap.

Approved by: cperciva (mentor)
Sponsored by: Amazon, Inc.

(cherry picked from commit 8cd86b51be4ab0fe70bad4830e608d56db5c850f)