mpc85xx: p2020: Fix nand driver probe

At this moment driver start fail with error:
[    3.771991] fsl,elbc-fcm-nand: probe of ffa00000.nand failed with error -22

elbc-fcm-nand driver use legacy method of ecc mode detection. It detect hw/sw
ecc mode when system configure it to "none". [1]

This patch adds 'nand-ecc-mode = "none"' propoerty to use generic driver
ecc mode detection.

[1] https://elixir.bootlin.com/linux/v5.10.18/source/drivers/mtd/nand/raw/fsl_elbc_nand.c#L730

Signed-off-by: Pawel Dembicki <paweldembicki@gmail.com>

target/linux/mpc85xx/patches-5.10/104-powerpc-mpc85xx-change-P2020RDB-dts-file-for-OpenWRT.patch

@@ -103,7 +103,15 @@ Signed-off-by: Pawel Dembicki <paweldembicki@gmail.com>
  			};
  		};
  
-@@ -140,13 +135,43 @@
+@@ -85,6 +80,7 @@
+                        compatible = "fsl,p2020-fcm-nand",
+                                     "fsl,elbc-fcm-nand";
+                        reg = <0x1 0x0 0x40000>;
++                       nand-ecc-mode = "none";
+
+                        partition@0 {
+                                /* This location must not be altered  */
+@@ -140,13 +136,43 @@
  	soc: soc@ffe00000 {
  		ranges = <0x0 0x0 0xffe00000 0x100000>;