configs/pandaboard: bump kernel and U-Boot versions

- Bump kernel to version 5.12.2.
- Bump U-Boot to version 2021.04.

While at it, enable VFPv3 with 32 registers (instead of 16) and add a few
comments to the defconfig.

Signed-off-by: Vincent Stehlé <vincent.stehle@laposte.net>
Cc: Peter Korsgaard <peter@korsgaard.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

configs/pandaboard_defconfig

@@ -1,32 +1,48 @@
+# Architecture
 BR2_arm=y
 BR2_cortex_a9=y
 BR2_ARM_ENABLE_NEON=y
 BR2_ARM_ENABLE_VFP=y
-BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_4_19=y
+BR2_ARM_FPU_VFPV3=y
+
+# Linux headers same as kernel, a 5.12 series
+BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_5_12=y
+
+# System
 BR2_ROOTFS_DEVICE_CREATION_DYNAMIC_MDEV=y
 BR2_TARGET_GENERIC_GETTY_PORT="ttyS2"
 BR2_SYSTEM_DHCP="eth0"
+
+# Image
 BR2_ROOTFS_POST_IMAGE_SCRIPT="support/scripts/genimage.sh"
 BR2_ROOTFS_POST_SCRIPT_ARGS="-c board/pandaboard/genimage.cfg"
+
+# Kernel
 BR2_LINUX_KERNEL=y
 BR2_LINUX_KERNEL_CUSTOM_VERSION=y
-BR2_LINUX_KERNEL_CUSTOM_VERSION_VALUE="4.19.62"
+BR2_LINUX_KERNEL_CUSTOM_VERSION_VALUE="5.12.2"
 BR2_LINUX_KERNEL_DEFCONFIG="omap2plus"
 BR2_LINUX_KERNEL_DTS_SUPPORT=y
 BR2_LINUX_KERNEL_INTREE_DTS_NAME="omap4-panda-es omap4-panda omap4-panda-a4"
 BR2_LINUX_KERNEL_INSTALL_TARGET=y
 BR2_LINUX_KERNEL_NEEDS_HOST_OPENSSL=y
+
+# Filesystem
 BR2_TARGET_ROOTFS_EXT2=y
 BR2_TARGET_ROOTFS_EXT2_4=y
 # BR2_TARGET_ROOTFS_TAR is not set
+
+# Bootloader
 BR2_TARGET_UBOOT=y
 BR2_TARGET_UBOOT_BUILD_SYSTEM_KCONFIG=y
 BR2_TARGET_UBOOT_CUSTOM_VERSION=y
-BR2_TARGET_UBOOT_CUSTOM_VERSION_VALUE="2017.05"
+BR2_TARGET_UBOOT_CUSTOM_VERSION_VALUE="2021.04"
 BR2_TARGET_UBOOT_BOARD_DEFCONFIG="omap4_panda"
 BR2_TARGET_UBOOT_FORMAT_IMG=y
 BR2_TARGET_UBOOT_SPL=y
 BR2_TARGET_UBOOT_SPL_NAME="MLO"
+
+# Required tools to create the SD card image
 BR2_PACKAGE_HOST_DOSFSTOOLS=y
 BR2_PACKAGE_HOST_GENIMAGE=y
 BR2_PACKAGE_HOST_MTOOLS=y