mediatek: mt7629: fix firmware partition

rename "kernel" partition in upstream dts to "firmware" and add
denx,fit as compatible string for mtdsplit.

Signed-off-by: Chuanhong Guo <gch981213@gmail.com>

target/linux/mediatek/patches-5.4/0010-dts-mt7629-rfb-fix-firmware-partition.patch

@@ -0,0 +1,13 @@
+--- a/arch/arm/boot/dts/mt7629-rfb.dts
++++ b/arch/arm/boot/dts/mt7629-rfb.dts
+@@ -163,8 +163,9 @@
+ 			};
+ 
+ 			partition@b0000 {
+-				label = "kernel";
++				label = "firmware";
+ 				reg = <0xb0000 0xb50000>;
++				compatible = "denx,fit";
+ 			};
+ 		};
+ 	};