dynamic_debug: consolidate repetitive struct _ddebug descriptor definitions

Replace the repetitive struct _ddebug descriptor definitions with a new
DECLARE_DYNAMIC_DEBUG_META_DATA(name, fmt) macro.

[akpm@linux-foundation.org: s/DECLARE/DEFINE/]
Signed-off-by: Jason Baron <jbaron@redhat.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>