tty: serial: jsm: fix two assignments in if conditions

Fixes two warnings reported of the form
"ERROR: do not use assignment in if condition"
reported by checkpatch.pl.
Signed-off-by: Alexander Vorwerk <alexander.vorwerk@stud.uni-goettingen.de>
Link: https://lore.kernel.org/r/20220315020745.15752-1-alexander.vorwerk@stud.uni-goettingen.deSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/jsm/jsm_neo.c

@@ -291,7 +291,8 @@ static void neo_copy_data_from_uart_to_queue(struct jsm_channel *ch)
 	ch->ch_cached_lsr = 0;
 
 	/* Store how much space we have left in the queue */
-	if ((qleft = tail - head - 1) < 0)
+	qleft = tail - head - 1;
+	if (qleft < 0)
 		qleft += RQUEUEMASK + 1;
 
 	/*

drivers/tty/serial/jsm/jsm_tty.c

@@ -749,7 +749,8 @@ void jsm_check_queue_flow_control(struct jsm_channel *ch)
 	int qleft;
 
 	/* Store how much space we have left in the queue */
-	if ((qleft = ch->ch_r_tail - ch->ch_r_head - 1) < 0)
+	qleft = ch->ch_r_tail - ch->ch_r_head - 1;
+	if (qleft < 0)
 		qleft += RQUEUEMASK + 1;
 
 	/*