drivers/net: Add Micrel KS8841/42 support to ks8842 driver

Body of the explanation:
   -support 16bit and 32bit bus width.
   -add device reset for ks8842/8841 Micrel device.
   -set 100Mbps as a default for Micrel device.
   -set MAC address in both MAC/Switch layer with different sequence for Micrel
    device, as mentioned in data sheet.
   -use private data to set options both 16/32bit bus width and Micrel device/
    Timberdale(FPGA).
   -update Kconfig in order to put more information about ks8842 device.

Signed-off-by: David J. Choi <david.choi@micrel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>