powerpc/85xx: introduce and document CONFIG_SYS_CCSRBAR macros

Introduce the CONFIG_SYS_CCSRBAR_PHYS_HIGH and CONFIG_SYS_CCSRBAR_PHYS_LOW
macros, which contain the high and low portions of CONFIG_SYS_CCSRBAR_PHYS.
This is necessary for the assembly-language code that relocates CCSR, since
the assembler does not understand 64-bit constants.

CONFIG_SYS_CCSRBAR_PHYS is automatically defined from the
CONFIG_SYS_CCSRBAR_PHYS_HIGH and CONFIG_SYS_CCSRBAR_PHYS_LOW macros, so it
should not be defined in a board header file.  Similarly,
CONFIG_SYS_CCSRBAR_DEFAULT is defined for each SOC in config_mpc85xx.h, so
it should also not be defined in the board header file.

CONFIG_SYS_CCSR_DO_NOT_RELOCATE is a "short-cut" macro that guarantees that
CONFIG_SYS_CCSRBAR_PHYS is set to the same value as CONFIG_SYS_CCSRBAR_DEFAULT,
and so CCSR will not be relocated.

Since CONFIG_SYS_CCSRBAR_DEFAULT is locked to a fixed value, multi-stage U-Boot
builds (e.g. NAND) are required to relocate CCSR only during the last stage
(i.e. the "real" U-Boot).  All other stages should define
CONFIG_SYS_CCSR_DO_NOT_RELOCATE to ensure that CCSR is not relocated.

README is updated with descriptions of all the CONFIG_SYS_CCSRBAR_xxx macros.

Signed-off-by: Timur Tabi <timur@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
diff --git a/include/configs/MPC8568MDS.h b/include/configs/MPC8568MDS.h
index f7df7f0..cf0ea47 100644
--- a/include/configs/MPC8568MDS.h
+++ b/include/configs/MPC8568MDS.h
@@ -71,14 +71,8 @@
 #define CONFIG_SYS_MEMTEST_START	0x00200000	/* memtest works on */
 #define CONFIG_SYS_MEMTEST_END		0x00400000
 
-/*
- * Base addresses -- Note these are effective addresses where the
- * actual resources get mapped (not physical addresses)
- */
-#define CONFIG_SYS_CCSRBAR_DEFAULT	0xff700000	/* CCSRBAR Default */
-#define CONFIG_SYS_CCSRBAR		0xe0000000	/* relocated CCSRBAR */
-#define CONFIG_SYS_CCSRBAR_PHYS	CONFIG_SYS_CCSRBAR	/* physical addr of CCSRBAR */
-#define CONFIG_SYS_IMMR		CONFIG_SYS_CCSRBAR	/* PQII uses CONFIG_SYS_IMMR */
+#define CONFIG_SYS_CCSRBAR		0xe0000000
+#define CONFIG_SYS_CCSRBAR_PHYS_LOW	CONFIG_SYS_CCSRBAR
 
 /* DDR Setup */
 #define CONFIG_FSL_DDR2