[libcalamares] Fix constness of functions

src/libcalamares/partition/PartitionQuery.cpp

@@ -27,14 +27,14 @@ using ::Device;
 using ::Partition;
 
 bool
-isPartitionFreeSpace( Partition* partition )
+isPartitionFreeSpace( const Partition* partition )
 {
     return partition->roles().has( PartitionRole::Unallocated );
 }
 
 
 bool
-isPartitionNew( Partition* partition )
+isPartitionNew( const Partition* partition )
 {
 #if defined( WITH_KPMCORE4API )
     constexpr auto NewState = Partition::State::New;

src/libcalamares/partition/PartitionQuery.h

@@ -34,14 +34,14 @@ using ::Device;
 using ::Partition;
 
 /** @brief Is this a free-space area? */
-bool isPartitionFreeSpace( Partition* );
+bool isPartitionFreeSpace( const Partition* );
 
 /** @brief Is this partition newly-to-be-created?
  *
  * Returns true if the partition is planned to be created by the installer as
  * opposed to already existing on the disk.
  */
-bool isPartitionNew( Partition* );
+bool isPartitionNew( const Partition* );
 
 /**
  * Iterates on all devices and return the first partition which is (already)