regmap: debugfs: Fix misuse of IS_ENABLED

IS_ENABLED should only be used for CONFIG_* symbols.

I have done a small test:
  #define REGMAP_ALLOW_WRITE_DEBUGFS
  IS_ENABLED(REGMAP_ALLOW_WRITE_DEBUGFS) returns 0.

  #define REGMAP_ALLOW_WRITE_DEBUGFS 0
  IS_ENABLED(REGMAP_ALLOW_WRITE_DEBUGFS) returns 0.

  #define REGMAP_ALLOW_WRITE_DEBUGFS 1
  IS_ENABLED(REGMAP_ALLOW_WRITE_DEBUGFS) returns 1.

  #define REGMAP_ALLOW_WRITE_DEBUGFS 2
  IS_ENABLED(REGMAP_ALLOW_WRITE_DEBUGFS) returns 0.

So fix the misuse of IS_ENABLED(REGMAP_ALLOW_WRITE_DEBUGFS) and switch to
use #if defined(REGMAP_ALLOW_WRITE_DEBUGFS) instead.
Signed-off-by: NAxel Lin <axel.lin@ingics.com>
Signed-off-by: NMark Brown <broonie@kernel.org>

drivers/base/regmap/regmap-debugfs.c

@@ -599,10 +599,11 @@ void regmap_debugfs_init(struct regmap *map, const char *name)
 	if (map->max_register || regmap_readable(map, 0)) {
 		umode_t registers_mode;
 
-		if (IS_ENABLED(REGMAP_ALLOW_WRITE_DEBUGFS))
+#if defined(REGMAP_ALLOW_WRITE_DEBUGFS)
 		registers_mode = 0600;
-		else
+#else
 		registers_mode = 0400;
+#endif
 
 		debugfs_create_file("registers", registers_mode, map->debugfs,
 				    map, &regmap_map_fops);