realtek: drop ethtool log noise

realtek: drop ethtool log noise

Demote a number of debugging printk's to pr_debug to avoid log
nosie.  Several of these functions are called as a result of
userspace activity.  This can cause a lot of log noise when
userspace does periodic polling.

Most of this could probably be removed completely, but let's
keep it for now since these drivers are still in development.

Signed-off-by: Bjørn Mork <bjorn@mork.no>
Tested-by: Stijn Tintel <stijn@linux-ipv6.be>
(cherry picked from commit ba220ad2fd915aaed2e9c850a84078c5c5977d3e)