Migrate the base and sub-options to Kconfig.  Note that we only enable
this in the base sandbox config now.

Cc: Alexey Brodkin <alexey.brodkin@gmail.com>
Cc: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: Tom Rini <trini@konsulko.com>
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Is this driver still used anywhere?  It's fishy that it's only enabled
in sandbox anymore.