meta-ohos-core: add a hardening option to the kernel

Add the hardening option CONFIG_DEBUG_CREDENTIALS to the kernel. It was
crashing at some point, but another check shows that this is not the case.

Signed-off-by: Marta Rybczynska <marta.rybczynska@huawei.com>

meta-ohos-core/recipes-kernel/linux/linux/hardening_validation_checks.cfg

@@ -6,7 +6,7 @@
 CONFIG_DEBUG_KERNEL=y
 
 # Validate common data structures
-# add CONFIG_DEBUG_CREDENTIALS=y
+CONFIG_DEBUG_CREDENTIALS=y
 CONFIG_DEBUG_NOTIFIERS=y
 CONFIG_DEBUG_LIST=y
 CONFIG_DEBUG_SG=y