Replace home-grown printk wrapper macros by ones from kernel.h and
device.h.

Also raise the log level in set_phy_reg() from debug to error because
these are really error conditions.  Could even be WARN_ON.  Lower the
log level in the device probe and driver shutdown from notice to info.
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>