parse-options.[ch]: revert use of "enum" for parse_options()

Revert the parse_options() prototype change in my recent
352e761388b (parse-options.[ch]: consistently use "enum
parse_opt_result", 2021-10-08) was incorrect. The parse_options()
function returns the number of argc elements that haven't been
processed, not "enum parse_opt_result".

Reported-by: SZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/parse-options.c b/parse-options.c
index 2a2c0ee..e788584 100644
--- a/parse-options.c
+++ b/parse-options.c
@@ -860,11 +860,11 @@ int parse_options_end(struct parse_opt_ctx_t *ctx)
 	return ctx->cpidx + ctx->argc;
 }
 
-enum parse_opt_result parse_options(int argc, const char **argv,
-				    const char *prefix,
-				    const struct option *options,
-				    const char * const usagestr[],
-				    enum parse_opt_flags flags)
+int parse_options(int argc, const char **argv,
+		  const char *prefix,
+		  const struct option *options,
+		  const char * const usagestr[],
+		  enum parse_opt_flags flags)
 {
 	struct parse_opt_ctx_t ctx;
 	struct option *real_options;