Kernel: Remove unused MemoryManager::m_physical_page_entries_free

Kernel/VM/MemoryManager.cpp

@@ -431,7 +431,6 @@ UNMAP_AFTER_INIT void MemoryManager::initialize_physical_pages()
     m_physical_page_entries = (PhysicalPageEntry*)range.value().base().get();
     for (size_t i = 0; i < m_physical_page_entries_count; i++)
         new (&m_physical_page_entries[i]) PageTableEntry();
-    m_physical_page_entries_free = m_physical_page_entries_count;
 
     // Now we should be able to allocate PhysicalPage instances,
     // so finish setting up the kernel page directory

Kernel/VM/MemoryManager.h

@@ -250,7 +250,6 @@ private:
     Vector<PhysicalRegion> m_super_physical_regions;
     Optional<PhysicalRegion> m_physical_pages_region;
     PhysicalPageEntry* m_physical_page_entries { nullptr };
-    size_t m_physical_page_entries_free { 0 };
     size_t m_physical_page_entries_count { 0 };
 
     Region::List m_user_regions;