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/powerpc/cpu/mpc8xx/start.S b/arch/powerpc/cpu/mpc8xx/start.S
index b8bdaae..ed735cd 100644
--- a/arch/powerpc/cpu/mpc8xx/start.S
+++ b/arch/powerpc/cpu/mpc8xx/start.S
@@ -322,7 +322,7 @@
 /*------------------------------------------------------------------------------*/
 
 /*
- * void relocate_code (addr_sp, gd, addr_moni)
+ * void relocate_code(addr_sp, gd, addr_moni)
  *
  * This "function" does not return, instead it continues in RAM
  * after relocating the monitor code.