gnu: libtasn1: Ungraft package.

* gnu/packages/tls.scm (libtasn1)[replacement]: Remove field.
[source]: Add patch.
(libtasn1/fixed): Remove variable.

gnu/packages/tls.scm

@@ -56,7 +56,6 @@
   (package
     (name "libtasn1")
     (version "4.12")
-    (replacement libtasn1/fixed)
     (source
      (origin
       (method url-fetch)
@@ -64,7 +63,8 @@
                           version ".tar.gz"))
       (sha256
        (base32
-        "0ls7jdq3y5fnrwg0pzhq11m21r8pshac2705bczz6mqjc8pdllv7"))))
+        "0ls7jdq3y5fnrwg0pzhq11m21r8pshac2705bczz6mqjc8pdllv7"))
+      (patches (search-patches "libtasn1-CVE-2017-10790.patch"))))
     (build-system gnu-build-system)
     (native-inputs `(("perl" ,perl)))
     (home-page "https://www.gnu.org/software/libtasn1/")
@@ -76,13 +76,6 @@ networking, allowing for formal validation of data according to some
 specifications.")
     (license license:lgpl2.0+)))
 
-(define libtasn1/fixed
-  (package
-    (inherit libtasn1)
-    (source (origin
-              (inherit (package-source libtasn1))
-              (patches (search-patches "libtasn1-CVE-2017-10790.patch"))))))
-
 (define-public asn1c
   (package
     (name "asn1c")