e1000e: use generic IEEE MII definitions

For standard IEEE MII-compatible transceivers, the kernel has generic
register and bit definitions.  Use those instead of redundant local
defines.

Do not replace references of MII_CR_SPEED_10 with BMCR_SPEED10 (0x0000)
when it is not necessary (i.e. when it is bitwise OR'ed with another
value).

Some whitespace issues in the surrounding context of the above changes are
also cleaned up.

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>