staging: mt7621-mmc: Fix warning when reloading module with debug msgs enabled

The kernel complained:

    [  510.277151] WARNING: CPU: 0 PID: 395 at fs/proc/generic.c:360 proc_register+0xf0/0x108
    [  510.292891] proc_dir_entry '/proc/msdc_debug' already registered

when doing a modprobe/rmmod/modprobe of this module if debug messages
are compiled in.  Fix this by removing the proc entry when the module is
unloaded.
Signed-off-by: George Hilliard <thirtythreeforty@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/mt7621-mmc/dbg.c

@@ -294,9 +294,18 @@ static const struct file_operations msdc_debug_fops = {
 	.release	= single_release,
 };
 
-void msdc_debug_proc_init(void)
+// Keep ahold of the proc entry we create so it can be freed during
+// module removal
+struct proc_dir_entry *msdc_debug_proc_entry;
+
+void __init msdc_debug_proc_init(void)
+{
+	msdc_debug_proc_entry = proc_create("msdc_debug", 0660,
+					    NULL, &msdc_debug_fops);
+}
+
+void __exit msdc_debug_proc_deinit(void)
 {
-	proc_create("msdc_debug", 0660, NULL, &msdc_debug_fops);
+	proc_remove(msdc_debug_proc_entry);
 }
-EXPORT_SYMBOL_GPL(msdc_debug_proc_init);
 #endif

drivers/staging/mt7621-mmc/dbg.h

@@ -92,8 +92,13 @@ enum msdc_dbg {
 #define DBG_EVT_MASK        (DBG_EVT_ALL)
 
 extern unsigned int sd_debug_zone[4];
-#define TAG "msdc"
-void msdc_debug_proc_init(void);
+#ifdef MT6575_SD_DEBUG
+void __init msdc_debug_proc_init(void);
+void __exit msdc_debug_proc_deinit(void);
+#else
+static inline void msdc_debug_proc_init(void) {}
+static inline void msdc_debug_proc_deinit(void) {}
+#endif
 
 u32 msdc_time_calc(u32 old_L32, u32 old_H32, u32 new_L32, u32 new_H32);
 void msdc_performance(u32 opcode, u32 sizes, u32 bRx, u32 ticks);

drivers/staging/mt7621-mmc/sd.c

@@ -1825,14 +1825,15 @@ static int __init mt_msdc_init(void)
 		return ret;
 	}
 
-#if defined(MT6575_SD_DEBUG)
 	msdc_debug_proc_init();
-#endif
+
 	return 0;
 }
 
 static void __exit mt_msdc_exit(void)
 {
+	msdc_debug_proc_deinit();
+
 	platform_driver_unregister(&mt_msdc_driver);
 }