fuzz/driver.c: appease -Wmissing-prototypes

Signed-off-by: NPatrick Steuer <patrick.steuer@de.ibm.com>
Reviewed-by: NRichard Levitte <levitte@openssl.org>
Reviewed-by: NKurt Roeckx <kurt@roeckx.be>
Reviewed-by: NNicola Tuveri <nic.tuv@gmail.com>
(Merged from https://github.com/openssl/openssl/pull/7138)

fuzz/driver.c

@@ -15,6 +15,9 @@
 
 #ifndef OPENSSL_NO_FUZZ_LIBFUZZER
 
+int LLVMFuzzerInitialize(int *argc, char ***argv);
+int LLVMFuzzerTestOneInput(const uint8_t *buf, size_t len);
+
 int LLVMFuzzerInitialize(int *argc, char ***argv)
 {
     return FuzzerInitialize(argc, argv);