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/arch/riscv/cpu/start.S b/arch/riscv/cpu/start.S
index 76850ec..f2ef556 100644
--- a/arch/riscv/cpu/start.S
+++ b/arch/riscv/cpu/start.S
@@ -13,6 +13,7 @@
 #include <config.h>
 #include <common.h>
 #include <elf.h>
+#include <system-constants.h>
 #include <asm/encoding.h>
 #include <generated/asm-offsets.h>
 
@@ -94,7 +95,7 @@
 #if defined(CONFIG_SPL_BUILD) && defined(CONFIG_SPL_STACK)
 	li	t1, CONFIG_SPL_STACK
 #else
-	li	t1, CONFIG_SYS_INIT_SP_ADDR
+	li	t1, SYS_INIT_SP_ADDR
 #endif
 	and	sp, t1, t0		/* force 16 byte alignment */