eCryptfs: fix compile error

This patch fixes the compile error reported at the address:

https://bugzilla.kernel.org/show_bug.cgi?id=40292

The problem arises when compiling eCryptfs as built-in and the 'encrypted'
key type as a module. The patch prevents this combination from being set in
the kernel configuration, by fixing the eCryptfs dependencies.
Signed-off-by: Roberto Sassu <roberto.sassu@polito.it>
Reported-by: David Hill <hilld@binarystorm.net>
Signed-off-by: Tyler Hicks <tyhicks@linux.vnet.ibm.com>

fs/ecryptfs/Kconfig

 config ECRYPT_FS
 	tristate "eCrypt filesystem layer support (EXPERIMENTAL)"
-	depends on EXPERIMENTAL && KEYS && CRYPTO
+	depends on EXPERIMENTAL && KEYS && CRYPTO && (ENCRYPTED_KEYS || ENCRYPTED_KEYS=n)
 	select CRYPTO_ECB
 	select CRYPTO_CBC
 	select CRYPTO_MD5