libpayload: Reintroduce CONFIG_LP_CHROMEOS to set suitable defaults

Chrome OS builds always have some inherent differences to "standard"
libpayload configurations: they don't want to use curses or things like
storage drivers, they always use the coreboot framebuffer and USB, etc.
This patch reintroduces CONFIG_LP_CHROMEOS as an option that only
affects Kconfig defaults. This allows Chrome OS builds to select most of
what they need in one go and reduces board-specific .config files to
only the options that are really specific to that board.

Also restricts the 8250_SERIAL_CONSOLE Kconfig to only default to yes on
x86 boards, which probably makes sense for all of libpayload (some but
far from all ARM boards use 8250-compatible UARTs, and we should
probably not default a platform option unless it's going to be correct
with very high probability).

BRANCH=None
BUG=None
TEST=Built and booted Jerry and Oak.

Change-Id: Ie0c0593ffd399608d2cbfb83d20891f6f1864914
Signed-off-by: Julius Werner <jwerner@chromium.org>
Original-Commit-Id: e558f59
Original-Change-Id: I609637cd2ea7dfb4558aa3c04c90b64038c9ab57
Original-Signed-off-by: Julius Werner <jwerner@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/347970
Original-Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/17024
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>

payloads/libpayload/drivers/storage/Kconfig

@@ -12,7 +12,7 @@
 
 config STORAGE
 	bool "Support for storage devices"
-	default y
+	default y if !CHROMEOS
 	help
 	  Select this option if you want support for storage devices (like
 	  hard drives, memory sticks or optical drives).