omap3: Definitions for SYS_BOOT-based fallback boot device selection

This introduces code to read the value of the SYS_BOOT pins on the OMAP3, as
well as the memory-preferred scheme for the interpretation of each value.

Signed-off-by: Paul Kocialkowski <contact@paulk.fr>
diff --git a/arch/arm/cpu/armv7/omap3/Makefile b/arch/arm/cpu/armv7/omap3/Makefile
index cf86046..b2fce96 100644
--- a/arch/arm/cpu/armv7/omap3/Makefile
+++ b/arch/arm/cpu/armv7/omap3/Makefile
@@ -8,6 +8,7 @@
 obj-y	:= lowlevel_init.o
 
 obj-y	+= board.o
+obj-y	+= boot.o
 obj-y	+= clock.o
 obj-y	+= sys_info.o
 ifdef CONFIG_SPL_BUILD