[partition] Fix size and last sector computation

Due to a computation error when calculating the total drive space and
each partition's last sector, the last partition's last sector was out
of boundaries, leading to an error creating this partition.

This patch fixes the computation algorithm to get rid of this error.

Signed-off-by: Arnaud Ferraris <arnaud.ferraris@collabora.com>

src/modules/partition/core/PartitionLayout.cpp

@@ -159,7 +159,7 @@ PartitionLayout::execute( Device *dev, qint64 firstSector,
 {
     QList< Partition* > partList;
     qint64 size, minSize, end;
-    qint64 totalSize = lastSector - firstSector;
+    qint64 totalSize = lastSector - firstSector + 1;
     qint64 availableSize = totalSize;
 
     // TODO: Refine partition sizes to make sure there is room for every partition
@@ -176,7 +176,7 @@ PartitionLayout::execute( Device *dev, qint64 firstSector,
             size = minSize;
         if ( size > availableSize )
             size = availableSize;
-        end = firstSector + size;
+        end = firstSector + size - 1;
 
         if ( luksPassphrase.isEmpty() )
         {