brcmfmac: add stub version of brcmf_debugfs_get_devdir()

In case of compiling driver without DEBUG expose a stub function to make
writing debug code much simpler (no extra conditions). This will allow
e.g. using debugfs_create_file() without any magic if or #ifdef.
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/broadcom/brcm80211/brcmfmac/debug.h

@@ -121,6 +121,10 @@ int brcmf_debugfs_add_entry(struct brcmf_pub *drvr, const char *fn,
 int brcmf_debug_create_memdump(struct brcmf_bus *bus, const void *data,
 			       size_t len);
 #else
+static inline struct dentry *brcmf_debugfs_get_devdir(struct brcmf_pub *drvr)
+{
+	return ERR_PTR(-ENOENT);
+}
 static inline
 int brcmf_debugfs_add_entry(struct brcmf_pub *drvr, const char *fn,
 			    int (*read_fn)(struct seq_file *seq, void *data))