media: pvrusb2: Fix incorrect variable used in trace message

The pvr2_trace message is reporting an error about control read
transfers, however it is using the incorrect variable write_len
instead of read_lean. Fix this by using the correct variable
read_len.

Fixes: d855497edbfb ("V4L/DVB (4228a): pvrusb2 to kernel 2.6.18")
Cc: [e-mail]
Signed-off-by: Colin Ian King <[e-mail]>
Signed-off-by: Hans Verkuil <[e-mail]>

drivers/media/usb/pvrusb2/pvrusb2-hdw.c

···
 		pvr2_trace(
 			PVR2_TRACE_ERROR_LEGS,
 			"Attempted to execute %d byte control-read transfer (limit=%d)",
-			write_len,PVR2_CTL_BUFFSIZE);
+			read_len, PVR2_CTL_BUFFSIZE);
 		return -EINVAL;
 	}
 	if ((!write_len) && (!read_len)) {