Migrate CUSTOM_SYS_INIT_SP_ADDR to Kconfig using system-constants.h

- Make all users of CUSTOM_SYS_INIT_SP_ADDR reference SYS_INIT_SP_ADDR
- Introduce HAS_CUSTOM_SYS_INIT_SP_ADDR to allow for setting the stack
  pointer directly, otherwise we use the common calculation.
- On some platforms that were using the standard calculation but did not
  set CONFIG_SYS_INIT_RAM_SIZE / CONFIG_SYS_INIT_RAM_ADDR, set them.
- On a small number of platforms that were not subtracting
  GENERATED_GBL_DATA_SIZE do so now via the standard calculation.
- CONFIG_SYS_INIT_SP_OFFSET is now widely unused, so remove it from most
  board config header files.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/include/configs/alt.h b/include/configs/alt.h
index eb71c6d..081e2a9 100644
--- a/include/configs/alt.h
+++ b/include/configs/alt.h
@@ -11,10 +11,9 @@
 
 #include "rcar-gen2-common.h"
 
-#define CONFIG_SYS_INIT_SP_ADDR		0x4f000000
 #define STACK_AREA_SIZE			0x00100000
 #define LOW_LEVEL_MERAM_STACK \
-		(CONFIG_SYS_INIT_SP_ADDR + STACK_AREA_SIZE - 4)
+		(SYS_INIT_SP_ADDR + STACK_AREA_SIZE - 4)
 
 /* MEMORY */
 #define RCAR_GEN2_SDRAM_BASE		0x40000000