base: Fix address range granularity calculations

This patch fixes a bug in the address range granularity
calculations. Previously it incorrectly used the high bit to establish
the size of the regions created, when it should really be looking at
the low bit.

src/base/addr_range.hh

@@ -140,7 +140,10 @@ class AddrRange
      *
      * @return The size of the regions created by the interleaving bits
      */
-    uint64_t granularity() const { return ULL(1) << intlvHighBit; }
+    uint64_t granularity() const
+    {
+        return ULL(1) << (intlvHighBit - intlvBits);
+    }
 
     /**
      * Determine the number of interleaved address stripes this range