x86/geode/alix2: Supplement driver to include GPIO button support

x86/geode/alix2: Supplement driver to include GPIO button support

GPIO 24 is used in reference designs as a soft-reset button, and
the alix2 is no exception.  Add it as a gpio-button.

Use symbolic values to describe BIOS addresses.

Record the model number.

Signed-off-by: Philip A. Prindeville <[email protected]>
Acked-by: Ed Wildgoose <[email protected]>
Acked-by: Andres Salomon <[email protected]>
Cc: Matthew Garrett <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Link: http://lkml.kernel.org/n/[email protected]
[ tidied up the code a bit ]
Signed-off-by: Ingo Molnar <[email protected]>