configs/ti_am62x_sk_defconfig: explicitly set the kernel version

Commit 4b8fddb060fb ("configs/ti_am62x_sk: new defconfig) forgot to
specify the Linux kernel version, so do that now.

When the defconfig was added, the default version was 6.4.x, so use
version 6.4.16.

Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
[Romain:
  use BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_6_4 as suggested
  by Giulio Benetti]
Signed-off-by: Romain Naour <romain.naour@smile.fr>

configs/ti_am62x_sk_defconfig

@@ -1,7 +1,10 @@
 BR2_aarch64=y
+BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_6_4=y
 BR2_ROOTFS_POST_IMAGE_SCRIPT="support/scripts/genimage.sh"
 BR2_ROOTFS_POST_SCRIPT_ARGS="-c board/ti/am62x-sk/genimage.cfg"
 BR2_LINUX_KERNEL=y
+BR2_LINUX_KERNEL_CUSTOM_VERSION=y
+BR2_LINUX_KERNEL_CUSTOM_VERSION_VALUE="6.4.16"
 BR2_LINUX_KERNEL_USE_ARCH_DEFAULT_CONFIG=y
 BR2_LINUX_KERNEL_DTS_SUPPORT=y
 BR2_LINUX_KERNEL_INTREE_DTS_NAME="ti/k3-am625-sk"