e1000e: adjust PM QoS request

It has been found that devices other than 82579 (a.k.a. e1000_pch2lan)
suffer from dropped transactions on platforms with deep C-states when
jumbo frames are enabled.  For example, LOMs on ICH9- and ICH10-based
platforms which recently had early-receive de-featured (for stability
reasons) suffer from this.  To resolve this for all devices, when jumbo
frames are enabled set the PM QoS DMA latency request based on the size
of the receive packet buffer less one full frame.

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>