[PATCH] dscc4: reset changes

[PATCH] dscc4: reset changes

From: Francois Romieu <romieu@fr.zoreil.com>

Workaround for lack of true reset:
- devices/ports are put in silent mode at ifconfig down time but some
  state is kept around to allow 'ifconfig up' issuing at a later time.
  Device specific structures are allocated when the pci asic is
  probed: dscc4_init_ring() moves from dscc4_open() to dscc4_found1().
- try to use reset related board-specific feature at module removal
  time if available. Comments in the code explain the whole story.
  Not a complicated feature but it is unavailable on the cards I own
  and no user gave me feedback -> currently untested.
  It shouldn't harm anyway.