Kernel: Memory-mapped files now have the absolute path as their name.

It's generated when the mapping is first created, so it won't update if
the file moves. Maybe that's something we should support, too.

Kernel/File.cpp

@@ -24,7 +24,7 @@ int File::ioctl(FileDescriptor&, unsigned, unsigned)
     return -ENOTTY;
 }
 
-KResultOr<Region*> File::mmap(Process&, LinearAddress, size_t, size_t, int)
+KResultOr<Region*> File::mmap(Process&, FileDescriptor&, LinearAddress, size_t, size_t, int)
 {
     return KResult(-ENODEV);
 }