[coreboot] [PATCH] Implement GPIO configuration options for Intel 3100 southbridge

[Ed Swierk]

When I originally ported the GPIO configuration routines for the Intel
3100 southbridge from esb6300_lpc.c, I left out the code that lets you
specify per-mainboard GPIO settings. This patch implements those
configuration routines, so you can put something like

register "gpio[23]" = "I3100_GPIO_USE_AS_GPIO |
I3100_GPIO_SEL_OUTPUT | I3100_GPIO_LVL_LOW"

in Config.lb to set GPIO 23 as an output, driving the signal low.

Signed-off-by: Ed Swierk