powerpc: mpc8xx: Change CONFIG_8xx to CONFIG_MPC8xx

CONFIG_8xx doesn't mean much outside of arch/powerpc/
This patch renames it CONFIG_MPC8xx just like CONFIG_MPC85xx etc ...
It also renames 8xx_immap.h to immap_8xx.h to be consistent with
other file names.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
diff --git a/include/ppc_asm.tmpl b/include/ppc_asm.tmpl
index 1878334..4947c77 100644
--- a/include/ppc_asm.tmpl
+++ b/include/ppc_asm.tmpl
@@ -81,7 +81,7 @@
 #define	r30	30
 #define	r31	31
 
-#if defined(CONFIG_8xx)
+#if defined(CONFIG_MPC8xx)
 
 /* Some special registers */
 
@@ -93,10 +93,10 @@
 #define LCTRL2	157	/* Load/Store Support	    (37-41) */
 #define ICTRL	158
 
-#endif	/* CONFIG_8xx */
+#endif	/* CONFIG_MPC8xx */
 
 
-#if defined(CONFIG_8xx)
+#if defined(CONFIG_MPC8xx)
 
 /* Registers in the processor's internal memory map that we use.
 */