vboot: split class in library and stage

The build system includes a bunch of files into verstage that
also exist in romstage - generic drivers etc.
These create link time conflicts when trying to link both the
verstage copy and romstage copy together in a combined configuration,
so separate "stage" parts (that allow things to run) from "library" parts
(that contain the vboot specifics).

Change-Id: Ieed910fcd642693e5e89e55f3e6801887d94462f
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Reviewed-on: http://review.coreboot.org/10041
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
diff --git a/src/soc/rockchip/rk3288/Makefile.inc b/src/soc/rockchip/rk3288/Makefile.inc
index be41327..0c7585a 100644
--- a/src/soc/rockchip/rk3288/Makefile.inc
+++ b/src/soc/rockchip/rk3288/Makefile.inc
@@ -39,7 +39,7 @@
 verstage-$(CONFIG_DRIVERS_UART) += uart.c
 verstage-y += gpio.c
 verstage-y += clock.c
-verstage-y += crypto.c
+libverstage-y += crypto.c
 verstage-y += i2c.c
 verstage-$(CONFIG_SOFTWARE_I2C) += software_i2c.c