staging: unisys: visorbus: convert client_bus_info sysfs to debugfs

staging: unisys: visorbus: convert client_bus_info sysfs to debugfs

Previously, the sysfs entry (assuming traditional sysfs mountpoint):

    /sys/bus/visorbus/devices/visorbus<n>/client_bus_info

violated kernel conventions by printing more than one item.  This along
with the fact that the data emitted was diagnostic data (intended to
shadow the client driver info provided via s-Par livedumps) made it a
logical candidate for debugfs.  So this patch moves this sysfs entry to
debugfs as (assuming traditional debugfs mountpoint):

    /sys/kernel/debug/visorbus/visorbus<n>/client_bus_info

Data for this debugfs is emitted using the preferred seq_file interface,
which allowed a vastly-simplified version of vbuschannel_print_devinfo()
to format the individual output components.

Functionality was verified as follows:

  [root@sparguest visorbus]# mount | grep debug
  debugfs on /sys/kernel/debug type debugfs (rw)
  [root@sparguest visorbus]# pwd
  /sys/kernel/debug/visorbus
  [root@sparguest visorbus]# l visorbus1/
  total 0
  drwxr-xr-x 2 root root 0 Sep 28 16:36 .
  drwxr-xr-x 4 root root 0 Sep 28 16:36 ..
  -r--r----- 1 root root 0 Sep 28 16:36 client_bus_info
  [root@sparguest visorbus]# l visorbus2
  total 0
  drwxr-xr-x 2 root root 0 Sep 28 16:36 .
  drwxr-xr-x 4 root root 0 Sep 28 16:36 ..
  -r--r----- 1 root root 0 Sep 28 16:36 client_bus_info
  [root@sparguest visorbus]# cat visorbus1/client_bus_info
  Client device / client driver info for s-Par Console partition (vbus #1):
     chipset          visorchipset     kernel ver. 4.8.0-rc6-ARCH+
     clientbus        visorbus         kernel ver. 4.8.0-rc6-ARCH+
  [2]keyboard         visorinput       kernel ver. 4.8.0-rc6-ARCH+
  [3]mouse            visorinput       kernel ver. 4.8.0-rc6-ARCH+
  [root@sparguest visorbus]# cat visorbus2/client_bus_info
  Client device / client driver info for s-Par IOVM partition (vbus #2):
     chipset          visorchipset     kernel ver. 4.8.0-rc6-ARCH+
     clientbus        visorbus         kernel ver. 4.8.0-rc6-ARCH+
  [0]ultravnic        visornic         kernel ver. 4.8.0-rc6-ARCH+
  [1]ultravnic        visornic         kernel ver. 4.8.0-rc6-ARCH+
  [2]sparvhba         visorhba         kernel ver. 4.8.0-rc6-ARCH+

Signed-off-by: Tim Sell <Timothy.Sell@unisys.com>
Reported-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: David Kershner <david.kershner@unisys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>