Upgrade password hashing algorithm

On my build host (NixOS unstable, soon-to-become 23.05), the host tools
use libxcrypt which does not support SHA-256 password hashing anymore.
Since SHA-512 is still supported and because that's something that
Buildroot also can work with, let's just switch this default in the
build image.

Bug: https://github.com/NixOS/nixpkgs/pull/220557
Change-Id: I2ca751b29afb7cf9885c81f0bfe9ee50f4c71baf
diff --git a/configs/czechlight_clearfog_defconfig b/configs/czechlight_clearfog_defconfig
index 561a561..37e5a12 100644
--- a/configs/czechlight_clearfog_defconfig
+++ b/configs/czechlight_clearfog_defconfig
@@ -14,6 +14,7 @@
 BR2_PER_PACKAGE_DIRECTORIES=y
 BR2_TARGET_GENERIC_HOSTNAME="czechlight"
 BR2_TARGET_GENERIC_ISSUE="Welcome to Czech Light"
+BR2_TARGET_GENERIC_PASSWD_SHA512=y
 BR2_INIT_SYSTEMD=y
 BR2_TARGET_GENERIC_GETTY_PORT="ttyS0"
 BR2_TARGET_GENERIC_GETTY_BAUDRATE_115200=y