That function is able to configure coalesce settings for an interface,
similarly to 'ethtool -C'.  This function also updates back the
structure so that it contains actual data on the device (if the device
doesn't support some settings kernel might just return 0 and not set
whatever is not supported), so this way we'll have up-to-date
information in the live domain XML.
Signed-off-by: NMartin Kletzander <mkletzan@redhat.com>