Adds GPIO customization for spacecast.

Since spacecast is a derivative of optimus. We will continue using
board-optimus.c. Use the config parameter CONFIG_GOOGLE_SPACECAST
to track spacecast specific customizations. The rule of thumb is to
minimize the use of CONFIG_GOOGLE_SPACECAST by using generic
definitions, e.g. TUNER_RESET_GPIO_PIN, to mark the hardware presence.

Change-Id: I97fa72b49054ae62956ed70b1fc37deefd22f328
3 files changed