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/mips/lib/reloc.c b/arch/mips/lib/reloc.c
index e68f494..1e3cfad 100644
--- a/arch/mips/lib/reloc.c
+++ b/arch/mips/lib/reloc.c
@@ -28,6 +28,7 @@
 
 #include <common.h>
 #include <cpu_func.h>
+#include <init.h>
 #include <asm/relocs.h>
 #include <asm/sections.h>