tty: n_gsm: Modify CR,PF bit printk info when config requester

When n_gsm config "initiator=0",as requester,gsmld receives dlci SABM/DISC
control command frame,UA frame printk info is error.

Example:
Gsmld send UA frame "f9 03 73 01 d7 f9",but CR,PF bit printk info
looks like error.

Kernel test log as follows:

Before modify

[   78.837626] c0 gsmld_receive: 00000000: f9 03 3f 01 1c f9
[   78.846356] c0 <-- 0) C: SABM(P)
[   78.854021] c0 gsmld_output: 00000000: f9 03 73 01 d7 f9
[   78.862574] c0 --> 0) C: UA(P)

After modify

[  261.233188] c0 gsmld_receive: 00000000: f9 03 3f 01 1c f9
[  261.242767] c0 <-- 0) C: SABM(P)
[  261.250497] c0 gsmld_output: 00000000: f9 03 73 01 d7 f9
[  261.259759] c0 --> 0) R: UA(F)

Signed-off-by: Zhenguo Zhao <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: Zhenguo Zhao

drivers/tty/n_gsm.c

@@ -587,6 +587,10 @@ static void gsm_send(struct gsm_mux *gsm, int addr, int cr, int control)
 		return;
 	}
 	gsmld_output(gsm, cbuf, len);
+	if (!gsm->initiator) {
+		cr = cr & gsm->initiator;
+		control = control & ~PF;
+	}
 	gsm_print_packet("-->", addr, cr, control, NULL, 0);
 }