fs: implement size/fatsize/ext4size

These commands may be used to determine the size of a file without
actually reading the whole file content into memory. This may be used
to determine if the file will fit into the memory buffer that will
contain it. In particular, the DFU code will use it for this purpose
in the next commit.

Signed-off-by: Stephen Warren <swarren@nvidia.com>

fs/ext4/ext4fs.c

@@ -182,6 +182,11 @@ int ext4fs_exists(const char *filename)
 	return file_len >= 0;
 }
 
+int ext4fs_size(const char *filename)
+{
+	return ext4fs_open(filename);
+}
+
 int ext4fs_read(char *buf, unsigned len)
 {
 	if (ext4fs_root == NULL || ext4fs_file == NULL)