common: Move relocate_code() to init.h

This is an init function so move it out of the common header. Avoid using
the typedef so that we don't have to include the global_data header file.

Also tidy up the function style in comments while we are here.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/nios2/cpu/start.S b/arch/nios2/cpu/start.S
index 2900200..f5ad184 100644
--- a/arch/nios2/cpu/start.S
+++ b/arch/nios2/cpu/start.S
@@ -147,7 +147,7 @@
 	 * We'll call the board_init_r from here since this isn't
 	 * supposed to return.
 	 *
-	 * void relocate_code (ulong sp, gd_t *global_data,
+	 * void relocate_code(ulong sp, gd_t *global_data,
 	 *			ulong reloc_addr)
 	 *			__attribute__ ((noreturn));
 	 */