axi: Add ihs_axi driver

Add a driver for the gdsys IHS AXI bus used on IHS FPGAs.

Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Mario Six <mario.six@gdsys.cc>
diff --git a/drivers/axi/Makefile b/drivers/axi/Makefile
index 100a777..18d9380 100644
--- a/drivers/axi/Makefile
+++ b/drivers/axi/Makefile
@@ -6,3 +6,4 @@
 #
 
 obj-$(CONFIG_AXI) += axi-uclass.o
+obj-$(CONFIG_IHS_AXI) += ihs_axi.o