Cleanup use of CONFIG_SYS_SRAM_BASE and CONFIG_SYS_SRAM_SIZE

Traditionally many boards used local definitions for SRAM base address
and size (like SRAM_BASE, SRAM_LEN and/or SRAM_SIZE), while the (now)
"official" names are CONFIG_SYS_SRAM_BASE and CONFIG_SYS_SRAM_SIZE.

The corresponding code in arch/powerpc/lib/board.c was board specific,
and has never actually been maintained well. Replace this by feature-
specific code and adapt the boards that actually use this.

NOTE: there is still a ton of boards using the old #defines, which
therefor contain incorrect values in bi_sramstart and bi_sramsize.

All respective board maintainers are requested to clean up their
respective configurations.  Thanks.

Signed-off-by: Wolfgang Denk <wd@denx.de>
Cc: Josef Wagner <Wagner@Microsys.de>
Cc: Stefan Roese <sr@denx.de>
Cc: Heiko Schocher <hs@denx.de>
Cc: Wolfgang Denk <wd@denx.de>
diff --git a/include/configs/IP860.h b/include/configs/IP860.h
index be63ea5..ed6b7fd 100644
--- a/include/configs/IP860.h
+++ b/include/configs/IP860.h
@@ -375,6 +375,8 @@
 #define SRAM_SIZE	(1 + (~(CONFIG_SYS_OR3 & BR_BA_MSK)))
 #define CONFIG_SYS_OR3_PRELIM	CONFIG_SYS_OR3			/* Make sure to map early */
 #define CONFIG_SYS_BR3_PRELIM	CONFIG_SYS_BR3			/* in case it's used for ENV */
+#define	CONFIG_SYS_SRAM_BASE	SRAM_BASE
+#define	CONFIG_SYS_SRAM_SIZE	SRAM_SIZE
 
 /*
  * BR4/OR4 - Board Control & Status (8 bit)