gpio: decouple tristate gpio support from board ID

This deprecates TERTIARY_BOARD_ID. Instead, a board will set
BOARD_ID_SUPPORT (the ones affected already do) which will set
GENERIC_GPIO_SUPPORT and compile the generic GPIO library.
The user is expected to handle the details of how the ID is encoded.

BUG=none
BRANCH=none
TEST=Compiled for peppy, nyan*, storm, and pinky

Change-Id: Iaf1cac6e90b6c931100e9d1b6735684fac86b8a8
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Original-Commit-Id: 93db63f419f596160ce2459eb70b3218cc83c09e
Original-Change-Id: I687877e5bb89679d0133bed24e2480216c384a1c
Original-Signed-off-by: David Hendricks <dhendrix@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/228322
Original-Reviewed-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: http://review.coreboot.org/9413
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

src/mainboard/google/nyan_big/Kconfig

@@ -34,7 +34,6 @@ config BOARD_SPECIFIC_OPTIONS # dummy
 	select SPI_FLASH
 	select SPI_FLASH_FAST_READ_DUAL_OUTPUT_3B
 	select VIRTUAL_DEV_SWITCH
-	select TERTIARY_BOARD_ID
 
 config MAINBOARD_DIR
 	string

src/mainboard/google/nyan_blaze/Kconfig

@@ -34,7 +34,6 @@ config BOARD_SPECIFIC_OPTIONS # dummy
 	select BOARD_ROMSIZE_KB_1024
 	select SPI_FLASH
 	select SPI_FLASH_FAST_READ_DUAL_OUTPUT_3B
-	select TERTIARY_BOARD_ID
 	select VIRTUAL_DEV_SWITCH
 
 config MAINBOARD_DIR

src/mainboard/google/rush_ryu/Kconfig

@@ -31,7 +31,6 @@ config BOARD_SPECIFIC_OPTIONS # dummy
 	select MAINBOARD_HAS_BOOTBLOCK_INIT
 	select BOARD_ROMSIZE_KB_4096
 	select VIRTUAL_DEV_SWITCH
-	select TERTIARY_BOARD_ID
 	select ARCH_SPINTABLE
 
 config MAINBOARD_DIR

src/mainboard/google/storm/Kconfig

@@ -28,7 +28,6 @@ config BOARD_SPECIFIC_OPTIONS
 	select MAINBOARD_HAS_BOOTBLOCK_INIT
 	select SPI_FLASH
 	select SPI_FLASH_SPANSION
-	select TERTIARY_BOARD_ID
 
 config BOARD_VARIANT_AP148
 	bool "pick this to build an image for ap148"