Revert "cdc_subset: deal with a device that needs reset for timeout"

This reverts commit 20fbe3ae.

As reported by Stephen Rothwell, it causes compile failures in certain
configurations:

  drivers/net/usb/cdc_subset.c:360:15: error: 'dummy_prereset' undeclared here (not in a function)
    .pre_reset = dummy_prereset,
                 ^
  drivers/net/usb/cdc_subset.c:361:16: error: 'dummy_postreset' undeclared here (not in a function)
    .post_reset = dummy_postreset,
                  ^

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Acked-by: David Miller <davem@davemloft.net>
Cc: Oliver Neukum <oneukum@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>