board/orangepi-zero-plus: bump Linux/U-Boot and switch to extlinux

Follow changes to other OrangePi boards, most importantly
orangepi-zero-plus2, which this board support is based on. This includes
switching to extlinux as boot mechanism and dropping custom U-Boot boot
script.

Rootfs image no longer fits into default 60M (mostly due to Linux
modules), so increase it to 120M.

While at it, bump Linux to 6.1.4 and U-Boot to 2023.01.

Signed-off-by: Marcin Niestroj <m.niestroj@grinn-global.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

board/orangepi/orangepi-zero-plus/boot.cmd

@@ -1,6 +0,0 @@
-setenv bootargs console=ttyS0,115200 earlyprintk root=/dev/mmcblk0p2 rootwait
-
-fatload mmc 0 $kernel_addr_r Image
-fatload mmc 0 $fdt_addr_r sun50i-h5-orangepi-zero-plus.dtb
-
-booti $kernel_addr_r - $fdt_addr_r

board/orangepi/orangepi-zero-plus/genimage.cfg

@@ -1,40 +0,0 @@
-image boot.vfat {
-	vfat {
-		files = {
-			"Image",
-			"sun50i-h5-orangepi-zero-plus.dtb",
-			"boot.scr"
-		}
-	}
-
-	size = 64M
-}
-
-image sdcard.img {
-	hdimage {
-	}
-
-	partition spl {
-		in-partition-table = "no"
-		image = "sunxi-spl.bin"
-		offset = 8K
-	}
-
-	partition u-boot {
-		in-partition-table = "no"
-		image = "u-boot.itb"
-		offset = 40K
-		size = 1M # 1MB - 40KB
-	}
-
-	partition boot {
-		partition-type = 0xC
-		bootable = "true"
-		image = "boot.vfat"
-	}
-
-	partition rootfs {
-		partition-type = 0x83
-		image = "rootfs.ext4"
-	}
-}