Fix broken CLIR in isdn driver

I noticed that CLIR (aka "hide your calling number") in isdn_tty is broken:
The at-command parser filters out the required "R" (e.g.  ATDR089123456)
It's been broken for a *very* long time.
Signed-off-by: NKarsten Keil <kkeil@suse.de>
Signed-off-by: NMatthias Goebl <matthias.goebl@goebl.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/isdn/i4l/isdn_tty.c

@@ -2693,8 +2693,9 @@ isdn_tty_getdial(char *p, char *q,int cnt)
 	int limit = ISDN_MSNLEN - 1;	/* MUST match the size of interface var to avoid
 					buffer overflow */
 
-	while (strchr(" 0123456789,#.*WPTS-", *p) && *p && --cnt>0) {
+	while (strchr(" 0123456789,#.*WPTSR-", *p) && *p && --cnt>0) {
 		if ((*p >= '0' && *p <= '9') || ((*p == 'S') && first) ||
+		    ((*p == 'R') && first) ||
 		    (*p == '*') || (*p == '#')) {
 			*q++ = *p;
 			limit--;