configs/imx6ulpico: bump U-Boot and kernel, switch to extlinux.conf

Current U-Boot is an old version and fails to build:

/usr/bin/ld: scripts/dtc/dtc-parser.tab.o:(.bss+0x10): multiple definition of `yylloc'; scripts/dtc/dtc-lexer.lex.o:(.bss+0x0): first defined here

Bump U-Boot to fix the problem.

Latest U-Boot has switched to distro boot and SPL, so make the necessary
changes to support it. Other advantage of bumping U-Boot is that
it also supports the other imx6ul-pico variants.

While at it, also bump U-Boot to the 5.15 LTS.

Fixes:
- https://gitlab.com/buildroot.org/buildroot/-/jobs/1915006192

Signed-off-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

board/technexion/imx6ulpico/rootfs_overlay/boot/extlinux/extlinux.conf

@@ -0,0 +1,4 @@
+Label imx6ul-pico-buildroot
+	kernel ../zImage
+	fdtdir ../
+	append root=PARTUUID=${uuid} rootwait rw console=${console},${baudrate}

configs/imx6ulpico_defconfig

@@ -3,8 +3,8 @@ BR2_arm=y
 BR2_cortex_a7=y
 BR2_ARM_FPU_NEON_VFPV4=y
 
-# Linux headers same as kernel, a 4.17 series
-BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_4_17=y
+# Linux headers same as kernel, a 5.15 series
+BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_5_15=y
 
 # system
 BR2_TARGET_GENERIC_GETTY_PORT="ttymxc5"
@@ -15,11 +15,12 @@ BR2_ROOTFS_OVERLAY="board/technexion/imx6ulpico/rootfs_overlay"
 # kernel
 BR2_LINUX_KERNEL=y
 BR2_LINUX_KERNEL_CUSTOM_VERSION=y
-BR2_LINUX_KERNEL_CUSTOM_VERSION_VALUE="4.17"
+BR2_LINUX_KERNEL_CUSTOM_VERSION_VALUE="5.15.11"
 BR2_LINUX_KERNEL_DEFCONFIG="imx_v6_v7"
 BR2_LINUX_KERNEL_DTS_SUPPORT=y
-BR2_LINUX_KERNEL_INTREE_DTS_NAME="imx6ul-pico-hobbit"
+BR2_LINUX_KERNEL_INTREE_DTS_NAME="imx6ul-pico-pi imx6ul-pico-hobbit imx6ul-pico-dwarf"
 BR2_LINUX_KERNEL_NEEDS_HOST_OPENSSL=y
+BR2_LINUX_KERNEL_INSTALL_TARGET=y
 
 # wifi firmware for brcm4339
 BR2_PACKAGE_LINUX_FIRMWARE=y
@@ -35,10 +36,13 @@ BR2_PACKAGE_WPA_SUPPLICANT_PASSPHRASE=y
 
 # bootloader
 BR2_TARGET_UBOOT=y
+BR2_TARGET_UBOOT_SPL=y
+BR2_TARGET_UBOOT_SPL_NAME="SPL"
 BR2_TARGET_UBOOT_BOARDNAME="pico-imx6ul"
 BR2_TARGET_UBOOT_CUSTOM_VERSION=y
-BR2_TARGET_UBOOT_CUSTOM_VERSION_VALUE="2018.05"
-BR2_TARGET_UBOOT_FORMAT_IMX=y
+BR2_TARGET_UBOOT_CUSTOM_VERSION_VALUE="2021.10"
+BR2_TARGET_UBOOT_NEEDS_OPENSSL=y
+BR2_TARGET_UBOOT_FORMAT_DTB_IMG=y
 
 # required tools to create the eMMC image
 BR2_PACKAGE_HOST_DOSFSTOOLS=y