git-compat-util.h: use "UNUSED", not "UNUSED(var)"

As reported in [1] the "UNUSED(var)" macro introduced in
2174b8c75de (Merge branch 'jk/unused-annotation' into next,
2022-08-24) breaks coccinelle's parsing of our sources in files where
it occurs.

Let's instead partially go with the approach suggested in [2] of
making this not take an argument. As noted in [1] "coccinelle" will
ignore such tokens in argument lists that it doesn't know about, and
it's less of a surprise to syntax highlighters.

This undoes the "help us notice when a parameter marked as unused is
actually use" part of 9b240347543 (git-compat-util: add UNUSED macro,
2022-08-19), a subsequent commit will further tweak the macro to
implement a replacement for that functionality.

1. https://lore.kernel.org/git/220825.86ilmg4mil.gmgdl@evledraar.gmail.com/
2. https://lore.kernel.org/git/220819.868rnk54ju.gmgdl@evledraar.gmail.com/

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/git-compat-util.h b/git-compat-util.h
index a969012..5ea7be9 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -190,9 +190,9 @@ struct strbuf;
 #define _SGI_SOURCE 1
 
 #if defined(__GNUC__)
-#define UNUSED(var) UNUSED_##var __attribute__((unused))
+#define UNUSED __attribute__((unused))
 #else
-#define UNUSED(var) UNUSED_##var
+#define UNUSED
 #endif
 
 #if defined(WIN32) && !defined(__CYGWIN__) /* Both MinGW and MSVC */
@@ -403,9 +403,9 @@ typedef uintmax_t timestamp_t;
 #endif
 
 #ifndef platform_core_config
-static inline int noop_core_config(const char *UNUSED(var),
-				   const char *UNUSED(value),
-				   void *UNUSED(cb))
+static inline int noop_core_config(const char *var UNUSED,
+				   const char *value UNUSED,
+				   void *cb UNUSED)
 {
 	return 0;
 }
@@ -499,7 +499,7 @@ static inline void extract_id_from_env(const char *env, uid_t *id)
 }
 
 static inline int is_path_owned_by_current_uid(const char *path,
-					       struct strbuf *UNUSED(report))
+					       struct strbuf *report UNUSED)
 {
 	struct stat st;
 	uid_t euid;