configs/imx6sx-sdb: bump U-Boot and kernel versions

Bump U-Boot to version 2021.07 and kernel to 5.10.55.

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

configs/imx6sx-sdb_defconfig

@@ -3,19 +3,19 @@ BR2_cortex_a9=y
 BR2_ARM_ENABLE_NEON=y
 BR2_ARM_ENABLE_VFP=y
 BR2_ARM_FPU_VFPV3=y
-# Linux headers same as kernel, a 4.14 series
-BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_4_14=y
+# Linux headers same as kernel, a 5.10 series
+BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_5_10=y
 BR2_TARGET_GENERIC_GETTY_PORT="ttymxc0"
 BR2_TARGET_ROOTFS_EXT2=y
 BR2_TARGET_ROOTFS_EXT2_4=y
 BR2_TARGET_UBOOT=y
 BR2_TARGET_UBOOT_BOARDNAME="mx6sxsabresd"
 BR2_TARGET_UBOOT_CUSTOM_VERSION=y
-BR2_TARGET_UBOOT_CUSTOM_VERSION_VALUE="2018.01"
+BR2_TARGET_UBOOT_CUSTOM_VERSION_VALUE="2021.07"
 BR2_TARGET_UBOOT_FORMAT_IMX=y
 BR2_LINUX_KERNEL=y
 BR2_LINUX_KERNEL_CUSTOM_VERSION=y
-BR2_LINUX_KERNEL_CUSTOM_VERSION_VALUE="4.14.14"
+BR2_LINUX_KERNEL_CUSTOM_VERSION_VALUE="5.10.55"
 BR2_LINUX_KERNEL_DEFCONFIG="imx_v6_v7"
 BR2_LINUX_KERNEL_DTS_SUPPORT=y
 BR2_LINUX_KERNEL_INTREE_DTS_NAME="imx6sx-sdb imx6sx-sdb-reva"