x86/geode/net5501: Add platform driver for Soekris Engineering net5501

Add platform driver for the Soekris Engineering net5501 single-board
computer.  Probes well-known locations in ROM for BIOS signature
to confirm correct platform.  Registers 1 LED and 1 GPIO-based
button (typically used for soft reset).

Signed-off-by: Philip Prindeville <philipp@redfish-solutions.com>
Acked-by: Alessandro Zummo <a.zummo@towertech.it>
Cc: Richard Purdie <rpurdie@rpsys.net>
Cc: Andres Salomon <dilinger@queued.net>
Cc: Matthew Garrett <mjg@redhat.com>
[ Removed Kconfig and Makefile detritus from drivers/leds/]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/n/tip-jv5uf34996juqh5syes8mn4h@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>