encrypted-keys: module build fixes

Encrypted keys are encrypted/decrypted using either a trusted or
user-defined key type, which is referred to as the 'master' key.
The master key may be of type trusted iff the trusted key is
builtin or both the trusted key and encrypted keys are built as
modules.  This patch resolves the build dependency problem.

- Use "masterkey-$(CONFIG_TRUSTED_KEYS)-$(CONFIG_ENCRYPTED_KEYS)" construct
to encapsulate the above logic. (Suggested by Dimtry Kasatkin.)
- Fixing the encrypted-keys Makefile, results in a module name change
from encrypted.ko to encrypted-keys.ko.
- Add module dependency for request_trusted_key() definition

Signed-off-by: Mimi Zohar <zohar@us.ibm.com>
diff --git a/security/keys/encrypted-keys/Makefile b/security/keys/encrypted-keys/Makefile
index 6bc7a86..d6f8433 100644
--- a/security/keys/encrypted-keys/Makefile
+++ b/security/keys/encrypted-keys/Makefile
@@ -2,5 +2,9 @@
 # Makefile for encrypted keys
-obj-$(CONFIG_ENCRYPTED_KEYS) += encrypted.o ecryptfs_format.o
-obj-$(CONFIG_TRUSTED_KEYS) += masterkey_trusted.o
+obj-$(CONFIG_ENCRYPTED_KEYS) += encrypted-keys.o
+encrypted-keys-y := encrypted.o ecryptfs_format.o
+masterkey-$(CONFIG_TRUSTED_KEYS) := masterkey_trusted.o
+masterkey-$(CONFIG_TRUSTED_KEYS)-$(CONFIG_ENCRYPTED_KEYS) := masterkey_trusted.o
+encrypted-keys-y += $(masterkey-y) $(masterkey-m-m)
diff --git a/security/keys/encrypted-keys/encrypted.h b/security/keys/encrypted-keys/encrypted.h
index b6ade89..8136a2d 100644
--- a/security/keys/encrypted-keys/encrypted.h
+++ b/security/keys/encrypted-keys/encrypted.h
@@ -2,7 +2,8 @@
 #define __ENCRYPTED_KEY_H
+#if defined(CONFIG_TRUSTED_KEYS) || \
 extern struct key *request_trusted_key(const char *trusted_desc,
 				       u8 **master_key, size_t *master_keylen);