Kernel: Make FS::block_size a size_t

Author: https://github.com/bugaevc
Commit: de4b7d9c21
Pull-request: https://github.com/SerenityOS/serenity/pull/2288
Reviewed-by: https://github.com/awesomekling

Kernel/FileSystem/ProcFS.cpp

@@ -742,7 +742,7 @@ Optional<KBuffer> procfs$df(InodeIdentifier)
         fs_object.add("total_inode_count", fs.total_inode_count());
         fs_object.add("free_inode_count", fs.free_inode_count());
         fs_object.add("mount_point", mount.absolute_path());
-        fs_object.add("block_size", fs.block_size());
+        fs_object.add("block_size", static_cast<u64>(fs.block_size()));
         fs_object.add("readonly", fs.is_readonly());
         fs_object.add("mount_flags", mount.flags());