crypto: xts - Add softdep on ecb

The xts module needs ecb to be present as it's meant to work
on top of ecb.  This patch adds a softdep so ecb can be included
automatically into the initramfs.
Reported-by: rftc <rftc@gmx.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/xts.c

@@ -466,3 +466,4 @@ MODULE_LICENSE("GPL");
 MODULE_DESCRIPTION("XTS block cipher mode");
 MODULE_ALIAS_CRYPTO("xts");
 MODULE_IMPORT_NS(CRYPTO_INTERNAL);
+MODULE_SOFTDEP("pre: ecb");