board_init: Change the logic to setup malloc_base

Prior to commit 5ba534d247 ("arm: Switch 32-bit ARM to using generic
global_data setup") we used to have assembly code that configured the
malloc_base address.

Since this commit we use the board_init_f_mem() function in C to setup
malloc_base address.

In board_init_f_mem() there was a deliberate choice to support only
early malloc() or full malloc() in SPL, but not both.

Adapt this logic to allow both to be used, one after the other, in SPL.

This issue has been observed in a Congatec board, where we need to
retrieve the manufacturing information from the SPI NOR (the SPI API
calls malloc) prior to configuring the DRAM. In this case as malloc_base
was not configured we always see malloc to fail.

With this change we are able to use malloc in SPL prior to DRAM gets
initialized.

Also update the CONFIG_SYS_SPL_MALLOC_START entry in the README file.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

README

@@ -3577,6 +3577,9 @@ FIT uImage format:
 
 		CONFIG_SYS_SPL_MALLOC_START
 		Starting address of the malloc pool used in SPL.
+		When this option is set the full malloc is used in SPL and
+		it is set up by spl_init() and before that, the simple malloc()
+		can be used if CONFIG_SYS_MALLOC_F is defined.
 
 		CONFIG_SYS_SPL_MALLOC_SIZE
 		The size of the malloc pool used in SPL.

common/init/board_init.c

@@ -50,8 +50,7 @@ ulong board_init_f_mem(ulong top)
 #endif
 	arch_setup_gd(gd_ptr);
 
-#if defined(CONFIG_SYS_MALLOC_F) && \
-	(!defined(CONFIG_SPL_BUILD) || !defined(CONFIG_SYS_SPL_MALLOC_START))
+#if defined(CONFIG_SYS_MALLOC_F)
 	top -= CONFIG_SYS_MALLOC_F_LEN;
 	gd->malloc_base = top;
 #endif