e1000: FIX: don't poke at manageability registers for incompatible adapters

The MANC register should not be read for PCI-E adapters at all, as well as
82543 and older where 82543 would master abort when this register was
accessed.

Signed-off-by: Auke Kok <auke-jan.h.kok@intel.com>
2 files changed