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/arch/powerpc/lib/board.c b/arch/powerpc/lib/board.c
index 628d067..80c1efc 100644
--- a/arch/powerpc/lib/board.c
+++ b/arch/powerpc/lib/board.c
@@ -519,15 +519,12 @@
 	bd->bi_memstart  = CONFIG_SYS_SDRAM_BASE;	/* start of  DRAM memory	*/
 	bd->bi_memsize   = gd->ram_size;	/* size  of  DRAM memory in bytes */
 
-#ifdef CONFIG_IP860
-	bd->bi_sramstart = SRAM_BASE;	/* start of  SRAM memory	*/
-	bd->bi_sramsize  = SRAM_SIZE;	/* size  of  SRAM memory	*/
-#elif defined CONFIG_MPC8220
+#ifdef CONFIG_SYS_SRAM_BASE
 	bd->bi_sramstart = CONFIG_SYS_SRAM_BASE;	/* start of  SRAM memory	*/
 	bd->bi_sramsize  = CONFIG_SYS_SRAM_SIZE;	/* size  of  SRAM memory	*/
 #else
-	bd->bi_sramstart = 0;		/* FIXME */ /* start of  SRAM memory	*/
-	bd->bi_sramsize  = 0;		/* FIXME */ /* size  of  SRAM memory	*/
+	bd->bi_sramstart = 0;
+	bd->bi_sramsize  = 0;
 #endif
 
 #if defined(CONFIG_8xx) || defined(CONFIG_8260) || defined(CONFIG_5xx) || \