xtest: copy dma-heap.h from Linux kernel v6.9

Copy the needed dma-heap.h from Linux kernel v6.9. This is a stable ABI
so it doesn't have to be synced with each new kernel.

dma-heap.h can be removed when the cross toolchains provide the file.

Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>
Reviewed-by: Joakim Bech <joakim.bech@linaro.org>
Acked-by: Jerome Forissier <jerome.forissier@linaro.org>
diff --git a/host/xtest/Makefile b/host/xtest/Makefile
index bd042d6..5959ed6 100644
--- a/host/xtest/Makefile
+++ b/host/xtest/Makefile
@@ -107,6 +107,7 @@
 
 CFLAGS += -I./
 CFLAGS += -I./adbg/include
+CFLAGS += -I./include/uapi
 CFLAGS += -I../supp_plugin/include
 CFLAGS += -I$(out-dir)/xtest