mISDN: Fix NULL pointer bug in if-condition of mISDN_dsp

Fix a bug (was introduced by a cut & paste error)
in cases when dsp->conf was NULL.
Signed-off-by: Andreas Eversberg <jolly@eversberg.eu>
Signed-off-by: Karsten Keil <keil@b1-systems.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/isdn/mISDN/dsp_cmx.c

@@ -1328,7 +1328,7 @@ dsp_cmx_send_member(struct dsp *dsp, int len, s32 *c, int members)
 		}
 		if (dsp->conf && dsp->conf->software && dsp->conf->hardware)
 			tx_data_only = 1;
-		if (dsp->conf->software && dsp->echo.hardware)
+		if (dsp->echo.software && dsp->echo.hardware)
 			tx_data_only = 1;
 	}