media: c8sectpfe: fix potential NULL pointer dereference in c8sectpfe_timer_interrupt

_channel_ is being dereferenced before it is null checked, hence there is a
potential null pointer dereference. Fix this by moving the pointer dereference
after _channel_ has been null checked.

This issue was detected with the help of Coccinelle.

Fixes: c5f5d0f9 ("[media] c8sectpfe: STiH407/10 Linux DVB demux support")
Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>
Acked-by: Patrice Chotard <patrice.chotard@st.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/platform/sti/c8sectpfe/c8sectpfe-core.c

@@ -83,7 +83,7 @@ static void c8sectpfe_timer_interrupt(struct timer_list *t)
 static void channel_swdemux_tsklet(unsigned long data)
 {
 	struct channel_info *channel = (struct channel_info *)data;
-	struct c8sectpfei *fei = channel->fei;
+	struct c8sectpfei *fei;
 	unsigned long wp, rp;
 	int pos, num_packets, n, size;
 	u8 *buf;
@@ -91,6 +91,8 @@ static void channel_swdemux_tsklet(unsigned long data)
 	if (unlikely(!channel || !channel->irec))
 		return;
 
+	fei = channel->fei;
+
 	wp = readl(channel->irec + DMA_PRDS_BUSWP_TP(0));
 	rp = readl(channel->irec + DMA_PRDS_BUSRP_TP(0));