KEYS: remove CONFIG_KEYS_COMPAT

KEYS_COMPAT now always takes the value of COMPAT && KEYS.  But the
security/keys/ directory is only compiled if KEYS is enabled, so in
practice KEYS_COMPAT is the same as COMPAT.  Therefore, remove the
unnecessary KEYS_COMPAT and just use COMPAT directly.

(Also remove an outdated comment from compat.c.)

Reviewed-by: James Morris <jamorris@linux.microsoft.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Tested-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>

security/keys/internal.h

@@ -264,7 +264,7 @@ extern long keyctl_dh_compute(struct keyctl_dh_params __user *, char __user *,
 			      size_t, struct keyctl_kdf_params __user *);
 extern long __keyctl_dh_compute(struct keyctl_dh_params __user *, char __user *,
 				size_t, struct keyctl_kdf_params *);
-#ifdef CONFIG_KEYS_COMPAT
+#ifdef CONFIG_COMPAT
 extern long compat_keyctl_dh_compute(struct keyctl_dh_params __user *params,
 				char __user *buffer, size_t buflen,
 				struct compat_keyctl_kdf_params __user *kdf);
@@ -279,7 +279,7 @@ static inline long keyctl_dh_compute(struct keyctl_dh_params __user *params,
 	return -EOPNOTSUPP;
 }
 
-#ifdef CONFIG_KEYS_COMPAT
+#ifdef CONFIG_COMPAT
 static inline long compat_keyctl_dh_compute(
 				struct keyctl_dh_params __user *params,
 				char __user *buffer, size_t buflen,