dax: Fix alloc_dax_region() compile warning

PFN flags are (unsigned long long), fix the alloc_dax_region() calling
convention to fix warnings of the form:

>> include/linux/pfn_t.h:18:17: warning: large integer implicitly truncated to unsigned type [-Woverflow]
    #define PFN_DEV (1ULL << (BITS_PER_LONG_LONG - 3))
Reported-by: Nkbuild test robot <lkp@intel.com>
Signed-off-by: NDan Williams <dan.j.williams@intel.com>
Acked-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/dax/bus.c

@@ -227,7 +227,7 @@ static void dax_region_unregister(void *region)
 
 struct dax_region *alloc_dax_region(struct device *parent, int region_id,
 		struct resource *res, int target_node, unsigned int align,
-		unsigned long pfn_flags)
+		unsigned long long pfn_flags)
 {
 	struct dax_region *dax_region;
 

drivers/dax/bus.h

@@ -11,7 +11,7 @@ struct dax_region;
 void dax_region_put(struct dax_region *dax_region);
 struct dax_region *alloc_dax_region(struct device *parent, int region_id,
 		struct resource *res, int target_node, unsigned int align,
-		unsigned long flags);
+		unsigned long long flags);
 
 enum dev_dax_subsys {
 	DEV_DAX_BUS,

drivers/dax/dax-private.h

@@ -32,7 +32,7 @@ struct dax_region {
 	struct device *dev;
 	unsigned int align;
 	struct resource res;
-	unsigned long pfn_flags;
+	unsigned long long pfn_flags;
 };
 
 /**