sf: Add spi_boot() to allow booting from SPI flash in an SPL

Signed-off-by: Christian Riesch <christian.riesch@omicron.at>
Cc: Heiko Schocher <hs@denx.de>
Cc: Mike Frysinger <vapier@gentoo.org>
Cc: Scott Wood <scottwood@freescale.com>
Acked-by: Mike Frysinger <vapier@gentoo.org>
diff --git a/drivers/mtd/spi/Makefile b/drivers/mtd/spi/Makefile
index 57112af..90f8392 100644
--- a/drivers/mtd/spi/Makefile
+++ b/drivers/mtd/spi/Makefile
@@ -25,6 +25,10 @@
 
 LIB	:= $(obj)libspi_flash.o
 
+ifdef CONFIG_SPL_BUILD
+COBJS-$(CONFIG_SPL_SPI_LOAD)	+= spi_spl_load.o
+endif
+
 COBJS-$(CONFIG_SPI_FLASH)	+= spi_flash.o
 COBJS-$(CONFIG_SPI_FLASH_ATMEL)	+= atmel.o
 COBJS-$(CONFIG_SPI_FLASH_EON)	+= eon.o