Determine GPIO base from /sys/class/gpio/gpiochip<N>
Determine GPIO base from /sys/class/gpio/gpiochip<N>

... instead of using hard-coded 192 constant.

BUG=chromium-os:19876
TEST=manual

If crossystem still reports correct values for devsw_cur recoverysw_cur (and
maybe wpsw_cur, although that's a separate bug), then it works.

Change-Id: Id8d4fb389bfd78f40da9ef08aa372071d77cbec1
Reviewed-on: http://gerrit.chromium.org/gerrit/7014
Reviewed-by: Bill Richardson <129945214b1d548d8e49b6c29c43094f8c78057f@chromium.org>
Tested-by: Bill Richardson <129945214b1d548d8e49b6c29c43094f8c78057f@chromium.org>

coreboot/vboot,geekboxzone/mmallow_external_vboot_reference,geekboxzone/mmallow_external_vboot_reference,ionave/seismograph,marineam/seismograph,geekboxzone/mmallow_external_vboot_reference,ionave/seismograph,ccaapton/vboot_reference,marineam/seismograph,coreboot/vboot,marineam/seismograph,acorn-marvell/vboot_reference,ccaapton/vboot_reference,coreboot/vboot,geekboxzone/mmallow_external_vboot_reference,ionave/seismograph,geekboxzone/mmallow_external_vboot_reference,acorn-marvell/vboot_reference,acorn-marvell/vboot_reference,acorn-marvell/vboot_reference,coreboot/vboot,ccaapton/vboot_reference,marineam/seismograph,coreboot/vboot,ccaapton/vboot_reference