e1000e: fix Rapid Start Technology support for i217

The definition of I217_PROXY_CTRL must use the BM_PHY_REG() macro instead
of the PHY_REG() macro for PHY page 800 register 70 since it is for a PHY
register greater than the maximum allowed by the latter macro, and fix a
typo setting the I217_MEMPWR register in e1000_suspend_workarounds_ich8lan.

Also for clarity, rename a few defines as bit definitions instead of masks.

Signed-off-by: Bruce Allan <bruce.w.allan@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>