e1000e: cleanup variables set but not used

The ICR register is clear on read and we don't care what the returned value
is when resetting the hardware so the icr variable(s) can be removed.  We
should not ignore the return from e1000_lv_jumbo_workaround_ich8lan() and
from e1000_get_phy_id_82571() (dump a debug message when it fails and when
an unknown Phy id is returned).

Signed-off-by: Bruce Allan <bruce.w.allan@intel.com>
Tested-by: Emil Tantilov <emil.s.tantilov@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>