fastboot: sparse: remove session-id logic

This "session-id" alogrithm is not required, and currently corrupts
the stored image whenever more the one "session" is required.

Signed-off-by: Steve Rae <srae@broadcom.com>

include/image-sparse.h

@@ -32,4 +32,4 @@ static inline int is_sparse_image(void *buf)
 }
 
 int store_sparse_image(sparse_storage_t *storage, void *storage_priv,
-		       unsigned int session_id, void *data);
+		       void *data);