sandbox: spi: Add SPI emulation bus

This adds a SPI framework for people to hook up simulated SPI clients.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/spi/Makefile b/drivers/spi/Makefile
index 27902fe..ed4ecd7 100644
--- a/drivers/spi/Makefile
+++ b/drivers/spi/Makefile
@@ -27,6 +27,7 @@
 obj-$(CONFIG_MXS_SPI) += mxs_spi.o
 obj-$(CONFIG_OC_TINY_SPI) += oc_tiny_spi.o
 obj-$(CONFIG_OMAP3_SPI) += omap3_spi.o
+obj-$(CONFIG_SANDBOX_SPI) += sandbox_spi.o
 obj-$(CONFIG_SOFT_SPI) += soft_spi.o
 obj-$(CONFIG_SH_SPI) += sh_spi.o
 obj-$(CONFIG_FSL_ESPI) += fsl_espi.o