common: Tidy up how malloc() is inited

The call to malloc() is a bit strange. The naming of the arguments
suggests that an address is passed, but in fact it is a pointer, at
least in the board_init_r() function and SPL equivalent.

Update it to work as described. Add a function comment as well.

Note that this does adjustment does not extend into the malloc()
implementation itself, apart from changing mem_malloc_init(), since
there are lots of casts and pointers and integers are used
interchangeably.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>

include/malloc.h

@@ -981,6 +981,14 @@ extern ulong mem_malloc_start;
 extern ulong mem_malloc_end;
 extern ulong mem_malloc_brk;
 
+/**
+ * mem_malloc_init() - Set up the malloc() pool
+ *
+ * Sets the region of memory to be used for all future calls to malloc(), etc.
+ *
+ * @start: Start address
+ * @size: Size in bytes
+ */
 void mem_malloc_init(ulong start, ulong size);
 
 #ifdef __cplusplus