Remove unused MAX_PARTS define

The MAX_PARTS define is not used anywhere in the source code and as
the MAX_PARTITIONS constant was introduced at the same time and used
to hold the same value it's most likely just a remainder from the
development of the partition support code.

Change-Id: I2ae8a062c5643839429f4e3e30a9af05597ce499
diff --git a/DirectVolume.h b/DirectVolume.h
index c0139d4..b7fea57 100644
--- a/DirectVolume.h
+++ b/DirectVolume.h
@@ -21,8 +21,6 @@
 
 #include "Volume.h"
 
-#define MAX_PARTS 4
-
 typedef android::List<char *> PathCollection;
 
 class DirectVolume : public Volume {