w1: mxc_w1: Fix incorrect "presence" status

W1 reset_bus() should return zero if slave device is present.
This patch fix this issue.
Signed-off-by: Alexander Shiyan <shc_work@mail.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/w1/masters/mxc_w1.c

@@ -66,7 +66,7 @@ static u8 mxc_w1_ds2_reset_bus(void *data)
 
 		udelay(100);
 	}
-	return !!(reg_val & MXC_W1_CONTROL_PST);
+	return !(reg_val & MXC_W1_CONTROL_PST);
 }
 
 /*