igb: fix two minor items found during code review

This patch addresses two minor items I found while cleaning up the igb
driver for our sourceforge version.

The first clears the context index if we don't flag that we need it.

The second item is that eims_other should be used instead of bit defines
when setting all of the EICS bits prior to reset.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>