tun: drop useless debugging statements

Some of the tun_debug() statements only inform us about entering
a function which can be easily achieved with ftrace or kprobe. As
tun_debug() is no-op unless TUN_DEBUG is set which requires editing the
source and recompiling, setting up ftrace or kprobe is easier. Drop these
debug statements.

Also drop the tun_debug() statement informing about SIOCSIFHWADDR ioctl.
We can monitor these through rtnetlink and it makes little sense to log
address changes through ioctl but not changes through rtnetlink. Moreover,
this tun_debug() is called even if the actual address change fails which
makes it even less useful.

Signed-off-by: Michal Kubecek <mkubecek@suse.cz>
Signed-off-by: David S. Miller <davem@davemloft.net>