e1000: make eeprom read/write scheduler friendly

Code was responsible for ~150ms scheduler latencies.

Signed-off-by: Joern Engel <joern@logfs.org>
Signed-off-by: Spencer Baugh <sbaugh@catern.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>