staging: unisys: add error messages to visornic

staging: unisys: add error messages to visornic

Add error message to genuine rare error paths, and debug messages
to enable relatively non-verbose tracing of code paths

You can enable debug messages by including this on the kernel command line:

    visornic.dyndbg=+p

or by this from the command line:

    echo "module visornic +p" > <debugfs>/dynamic_debug/control

Refer to Documentation/dynamic-debug-howto.txt for more details.

In addition to the new debug and error messages, a message like the
following will be logged every time a visornic device is probed, which
will enable you to map back-and-forth between visorbus device names
(e.g., "vbus2:dev0") and netdev names (e.g., "eth0"):

    visornic vbus2:dev0: visornic_probe success netdev=eth0

With this patch and visornic debugging enabled, you should expect to see
messages like the following in the most-common scenarios:

* driver loaded:

      visornic_init

* device probed:

      visornic vbus2:dev0: visornic_probe
      visor_thread_start
      visor_thread_start success

* network interface configured (ifconfig):

      net eth0: visornic_open
      net eth0: visornic_enable_with_timeout
      net eth0: visornic_enable_with_timeout success
      net eth0: visornic_open success

Signed-off-by: Tim Sell <Timothy.Sell@unisys.com>
Signed-off-by: Benjamin Romer <benjamin.romer@unisys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>