imx8qm: mek: enable dm-spl for pm

with u-boot,dm-spl added for imx8qm-pm node, and SPL_SIMPLE_BUS enabled,
the bind and probe code in board file could be removed.

Also we need to enlarge SYS_MALLOC_F_LEN to avoid calloc fail.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
diff --git a/arch/arm/dts/fsl-imx8qm-mek-u-boot.dtsi b/arch/arm/dts/fsl-imx8qm-mek-u-boot.dtsi
index 5d50eb0..9a4a83b 100644
--- a/arch/arm/dts/fsl-imx8qm-mek-u-boot.dtsi
+++ b/arch/arm/dts/fsl-imx8qm-mek-u-boot.dtsi
@@ -3,6 +3,11 @@
  * Copyright 2018 NXP
  */
 
+&{/imx8qm-pm} {
+
+	u-boot,dm-spl;
+};
+
 &mu {
 	u-boot,dm-spl;
 };