Fix -Wformat-nonliteral violation in ssl_cipher.c.

Besides avoiding the -Wformat-nonliteral warning, it is easier to
review (changes to) the code when the format string is passed to the
function as a literal.

Change-Id: I5093ad4494d5ebeea3f2671509b916cd6c5fb173
Reviewed-on: https://boringssl-review.googlesource.com/6908
Reviewed-by: David Benjamin <davidben@google.com>

ssl/ssl_cipher.c

diff --git a/ssl/ssl_cipher.c b/ssl/ssl_cipher.c
index 77fa8fa..ba73848 100644
--- a/ssl/ssl_cipher.c
+++ b/ssl/ssl_cipher.c
@@ -1804,7 +1804,6 @@
                                    int len) {
   const char *kx, *au, *enc, *mac;
   uint32_t alg_mkey, alg_auth, alg_enc, alg_mac;
-  static const char *format = "%-23s Kx=%-8s Au=%-4s Enc=%-9s Mac=%-4s\n";
 
   alg_mkey = cipher->algorithm_mkey;
   alg_auth = cipher->algorithm_auth;
@@ -1928,7 +1927,8 @@
     return "Buffer too small";
   }
 
-  BIO_snprintf(buf, len, format, cipher->name, kx, au, enc, mac);
+  BIO_snprintf(buf, len, "%-23s Kx=%-8s Au=%-4s Enc=%-9s Mac=%-4s\n",
+               cipher->name, kx, au, enc, mac);
   return buf;
 }