net: Add SMC911X driver to Kconfig, convert

We add the various SMC91XX symbols to drivers/net/Kconfig and then this
converts the following to Kconfig:
   CONFIG_SMC911X
   CONFIG_SMC911X_BASE
   CONFIG_SMC911X_16_BIT
   CONFIG_SMC911X_32_BIT

Signed-off-by: Adam Ford <aford173@gmail.com>
[trini: Apply to the rest of the tree, re-squash old and new patch]
Signed-off-by: Tom Rini <trini@konsulko.com>