ixgbe: move all GPIE register config into a single function

This change moves all GPIE register configuration into a single function.
The advantage of this is that we can avoid a number of unnecessary
read/modify/write cycles on the register.

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>