dynamic_debug: describe_flags with '=[pmflt_]*'

Change describe_flags() to emit '=[pmflt_]+' for current callsite
flags, or just '=_' when they're disabled.  Having '=' in output
allows a more selective grep expression; in contrast '-' may appear
in filenames, line-ranges, and format-strings.  '=' also has better
mnemonics, saying; "the current setting is equal to <flags>".

This allows grep "=_" <dbgfs>/dynamic_debug/control to see disabled
callsites while avoiding the many occurrences of " = " seen in format
strings.

Enlarge flagsbufs to handle additional flag char, and alter
ddebug_parse_flags() to allow flags=0, so that user can turn off all
debug flags via:

  ~# echo =_ > <dbgfs>/dynamic_debug/control

Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
Signed-off-by: Jason Baron <jbaron@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h
index 29ea09a..fc39640 100644
--- a/include/linux/dynamic_debug.h
+++ b/include/linux/dynamic_debug.h
@@ -21,7 +21,8 @@
  	 * The bits here are changed dynamically when the user
 	 * writes commands to <debugfs>/dynamic_debug/control
 	 */
-#define _DPRINTK_FLAGS_PRINT   (1<<0)  /* printk() a message using the format */
+#define _DPRINTK_FLAGS_NONE	0
+#define _DPRINTK_FLAGS_PRINT	(1<<0) /* printk() a message using the format */
 #define _DPRINTK_FLAGS_INCL_MODNAME	(1<<1)
 #define _DPRINTK_FLAGS_INCL_FUNCNAME	(1<<2)
 #define _DPRINTK_FLAGS_INCL_LINENO	(1<<3)