tracing/events: Fix swiotlb tracepoint creation

Tracepoints are only created when Xen support is enabled, but they are
also referenced within lib/swiotlb.c. So unless Xen support is enabled
the tracepoints will be missing, therefore causing builds to fail. Fix
this by moving the tracepoint creation to lib/swiotlb.c, which works
nicely because the Xen swiotlb support selects the generic swiotlb
support.
Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

drivers/xen/swiotlb-xen.c

@@ -43,7 +43,6 @@
 #include <xen/xen-ops.h>
 #include <xen/hvc-console.h>
 
-#define CREATE_TRACE_POINTS
 #include <trace/events/swiotlb.h>
 /*
  * Used to do a quick range check in swiotlb_tbl_unmap_single and

lib/swiotlb.c

@@ -38,6 +38,7 @@
 #include <linux/bootmem.h>
 #include <linux/iommu-helper.h>
 
+#define CREATE_TRACE_POINTS
 #include <trace/events/swiotlb.h>
 
 #define OFFSET(val,align) ((unsigned long)	\