[PATCH] e1000: narrow down the scope of the tipg timer tweak

the driver has (ancient) code for messing with TIPG from the 82542 days.
Unfortunately this code was running on our current adapters and setting
TIPG for fiber to be +1 over the copper value.  This caused 1.45Mpps
to be sent instead of 1.487Mpps.

Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: Auke Kok <auke-jan.h.kok@intel.com>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>