xen: Fix Kconfig dependencies

XEN config can be enabled by other platforms (even it doesn't need to make
sense) that's why fix dependencies. XEN (xenbus.c) requires sscanf (also
pvblock needs it). And PVBLOCK is inside drivers/xen folder which requires
XEN to be enabled.

Signed-off-by: Michal Simek <michal.simek@amd.com>
Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
diff --git a/Kconfig b/Kconfig
index f24e4f0..b4de17a 100644
--- a/Kconfig
+++ b/Kconfig
@@ -175,6 +175,7 @@
 
 config XEN
 	bool "Select U-Boot be run as a bootloader for XEN Virtual Machine"
+	select SSCANF
 	help
 	  Enabling this option will make U-Boot be run as a bootloader
 	  for XEN [1] Virtual Machine.
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index d7e6578..ab22c0e 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -2044,7 +2044,6 @@
 	select OF_CONTROL
 	select LINUX_KERNEL_IMAGE_HEADER
 	select XEN_SERIAL
-	select SSCANF
 	imply OF_HAS_PRIOR_STAGE
 
 config ARCH_GXP
diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig
index 0ee74d0..6cb9149 100644
--- a/drivers/xen/Kconfig
+++ b/drivers/xen/Kconfig
@@ -1,6 +1,6 @@
 config PVBLOCK
 	bool "Xen para-virtualized block device"
-	depends on DM
+	depends on DM && XEN
 	select BLK
 	help
 	  This driver implements the front-end of the Xen virtual