Added dmesg security restriction.

This has been enabled in generic kernels of Ubuntu. If enabled, dmesg will now be run only as root.

Author: AdityaGarg8

templates/default-config

@@ -9968,7 +9968,7 @@ CONFIG_BIG_KEYS=y
 CONFIG_TRUSTED_KEYS=m
 CONFIG_ENCRYPTED_KEYS=m
 CONFIG_KEY_DH_OPERATIONS=y
-# CONFIG_SECURITY_DMESG_RESTRICT is not set
+CONFIG_SECURITY_DMESG_RESTRICT=y
 CONFIG_SECURITY=y
 CONFIG_SECURITYFS=y
 CONFIG_SECURITY_NETWORK=y