xen/setup: Ignore E820_UNUSABLE when setting 1-1 mappings.

When we parse the raw E820, the Xen hypervisor can set "E820_RAM"
to "E820_UNUSABLE" if the mem=X argument is used. As such we
should _not_ consider the E820_UNUSABLE as an 1-1 identity
mapping, but instead use the same case as for E820_RAM.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index 90bac0a..fba4a6c 100644
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -166,7 +166,7 @@
 		if (last > end)
 			continue;
 
-		if (entry->type == E820_RAM) {
+		if ((entry->type == E820_RAM) || (entry->type == E820_UNUSABLE)) {
 			if (start > start_pci)
 				identity += set_phys_range_identity(
 						PFN_UP(start_pci), PFN_DOWN(start));