libmbedtls: Use single-line string literals.

Signed-off-by: Guido Vranken <guidovranken@gmail.com>
[Cherry-pick upstream commit 962e4ee4a6b3, add libmbedtls: prefix]
Signed-off-by: Jerome Forissier <jerome@forissier.org>
diff --git a/lib/libmbedtls/mbedtls/library/sha512.c b/lib/libmbedtls/mbedtls/library/sha512.c
index 1c74991..d5a5b51 100644
--- a/lib/libmbedtls/mbedtls/library/sha512.c
+++ b/lib/libmbedtls/mbedtls/library/sha512.c
@@ -522,8 +522,7 @@
 static const unsigned char sha512_test_buf[3][113] =
 {
     { "abc" },
-    { ("abcdefghbcdefghicdefghijdefghijkefghijklfghijklmghijklmn"
-      "hijklmnoijklmnopjklmnopqklmnopqrlmnopqrsmnopqrstnopqrstu") },
+    { "abcdefghbcdefghicdefghijdefghijkefghijklfghijklmghijklmnhijklmnoijklmnopjklmnopqklmnopqrlmnopqrsmnopqrstnopqrstu" },
     { "" }
 };