drivers: Add SPMI bus uclass

Qualcom processors use proprietary bus to talk with PMIC devices -
SPMI (System Power Management Interface).
On wiring level it is similar to I2C, but on protocol level, it's
multi-master and has simple autodetection capabilities.
This commit adds simple uclass that provides bus read/write interface.

Signed-off-by: Mateusz Kulikowski <mateusz.kulikowski@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Tested-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/spmi/Makefile b/drivers/spmi/Makefile
new file mode 100644
index 0000000..99092eb
--- /dev/null
+++ b/drivers/spmi/Makefile
@@ -0,0 +1,7 @@
+#
+# (C) Copyright 2015 Mateusz Kulikowski <mateusz.kulikowski@gmail.com>
+#
+# SPDX-License-Identifier:	GPL-2.0+
+#
+
+obj-$(CONFIG_SPMI)  += spmi-uclass.o