xen: Port Xen bus driver from mini-os

Make required updates to run on u-boot and strip test code.

Signed-off-by: Anastasiia Lukianenko <anastasiia_lukianenko@epam.com>
Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 0c1b754..8401851 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1756,6 +1756,7 @@
 	select OF_CONTROL
 	select LINUX_KERNEL_IMAGE_HEADER
 	select XEN_SERIAL
+	select SSCANF
 endchoice
 
 config ARCH_SUPPORT_TFABOOT