Retrofit devices do not do allocatable space / 2.

Retrofit devices have two supers, so the allocatable
space does not need to be halved.

Test: manual OTA
Bug: 118506262
Change-Id: I31c77b9318e7c0b6bc6d1a8ae6efa70a3383b05f
diff --git a/dynamic_partition_control_interface.h b/dynamic_partition_control_interface.h
index b92d88a..86a0730 100644
--- a/dynamic_partition_control_interface.h
+++ b/dynamic_partition_control_interface.h
@@ -35,6 +35,9 @@
   // Return true iff dynamic partitions is enabled on this device.
   virtual bool IsDynamicPartitionsEnabled() = 0;
 
+  // Return true iff dynamic partitions is retrofitted on this device.
+  virtual bool IsDynamicPartitionsRetrofit() = 0;
+
   // Map logical partition on device-mapper.
   // |super_device| is the device path of the physical partition ("super").
   // |target_partition_name| is the identifier used in metadata; for example,