bus: Optionally include TI sysc driver in SPL/TPL

The TI sysc bus driver is required to allow access to the SPI bus on
am335x platforms. To support SPI boot this driver needs to be enabled in
the SPL/TPL as appropriate.

Signed-off-by: Paul Barker <paul.barker@sancloud.com>
diff --git a/drivers/Makefile b/drivers/Makefile
index ac2d83a..6f1de58 100644
--- a/drivers/Makefile
+++ b/drivers/Makefile
@@ -37,6 +37,7 @@
 obj-$(CONFIG_$(SPL_TPL_)TPM) += tpm/
 obj-$(CONFIG_XEN) += xen/
 obj-$(CONFIG_$(SPL_)FPGA) += fpga/
+obj-y += bus/
 
 ifndef CONFIG_TPL_BUILD
 ifndef CONFIG_VPL_BUILD
@@ -77,7 +78,6 @@
 
 obj-y += adc/
 obj-y += ata/
-obj-y += bus/
 obj-$(CONFIG_DM_DEMO) += demo/
 obj-$(CONFIG_BIOSEMU) += bios_emulator/
 obj-y += block/