spl: Use SYS_MALLOC_F instead of SYS_MALLOC_F_LEN

Use the new SPL/TPL/VPL_SYS_MALLOC_F symbols to determine whether the
malloc pool exists.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Sean Anderson <sean.anderson@seco.com>
diff --git a/arch/mips/cpu/start.S b/arch/mips/cpu/start.S
index 2acc21d..a95c95b 100644
--- a/arch/mips/cpu/start.S
+++ b/arch/mips/cpu/start.S
@@ -46,7 +46,7 @@
 		sp, sp, GD_SIZE		# reserve space for gd
 	and	sp, sp, t0		# force 16 byte alignment
 	move	k0, sp			# save gd pointer
-#if CONFIG_VAL(SYS_MALLOC_F_LEN) && \
+#if CONFIG_IS_ENABLED(SYS_MALLOC_F) && \
     !CONFIG_IS_ENABLED(INIT_STACK_WITHOUT_MALLOC_F)
 	li	t2, CONFIG_VAL(SYS_MALLOC_F_LEN)
 	PTR_SUBU \
@@ -63,7 +63,7 @@
 	blt	t0, t1, 1b
 	 nop
 
-#if CONFIG_VAL(SYS_MALLOC_F_LEN) && \
+#if CONFIG_IS_ENABLED(SYS_MALLOC_F) && \
     !CONFIG_IS_ENABLED(INIT_STACK_WITHOUT_MALLOC_F)
 	PTR_S	sp, GD_MALLOC_BASE(k0)	# gd->malloc_base offset
 #endif