spl: make SPL and normal u-boot stage use independent SYS_MALLOC_F_LEN

Some platforms have very limited SRAM to run SPL code, so there may
not be the same amount space for a malloc pool before relocation in
the SPL stage as the normal U-Boot stage.

Make SPL and (the full) U-Boot stage use independent SYS_MALLOC_F_LEN,
so the size of pre-relocation malloc pool can be configured memory
space independently.

Signed-off-by: Andy Yan <andy.yan@rock-chips.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Acked-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
[fixed up commit-message:]
Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
diff --git a/drivers/core/Kconfig b/drivers/core/Kconfig
index fb5c4e8..f8b19a4 100644
--- a/drivers/core/Kconfig
+++ b/drivers/core/Kconfig
@@ -16,10 +16,10 @@
 	  suitable malloc() implementation. If you are not using the
 	  full malloc() enabled by CONFIG_SYS_SPL_MALLOC_START,
 	  consider using CONFIG_SYS_MALLOC_SIMPLE. In that case you
-	  must provide CONFIG_SYS_MALLOC_F_LEN to set the size.
+	  must provide CONFIG_SPL_SYS_MALLOC_F_LEN to set the size.
 	  In most cases driver model will only allocate a few uclasses
 	  and devices in SPL, so 1KB should be enable. See
-	  CONFIG_SYS_MALLOC_F_LEN for more details on how to enable it.
+	  CONFIG_SPL_SYS_MALLOC_F_LEN for more details on how to enable it.
 
 config TPL_DM
 	bool "Enable Driver Model for TPL"
@@ -29,10 +29,10 @@
 	  suitable malloc() implementation. If you are not using the
 	  full malloc() enabled by CONFIG_SYS_SPL_MALLOC_START,
 	  consider using CONFIG_SYS_MALLOC_SIMPLE. In that case you
-	  must provide CONFIG_SYS_MALLOC_F_LEN to set the size.
+	  must provide CONFIG_SPL_SYS_MALLOC_F_LEN to set the size.
 	  In most cases driver model will only allocate a few uclasses
 	  and devices in SPL, so 1KB should be enough. See
-	  CONFIG_SYS_MALLOC_F_LEN for more details on how to enable it.
+	  CONFIG_SPL_SYS_MALLOC_F_LEN for more details on how to enable it.
 	  Disable this for very small implementations.
 
 config DM_WARN