dmaengine: ste_dma40: Fetch the number of physical channels from DT

Some platforms insist on obscure physical channel availability. This
information is currently passed though platform data in internal BSP
kernels. Once those platforms land, they'll need to configure them
appropriately, so we may as well add the infrastructure.

Cc: Dan Williams <[e-mail]>
Cc: Per Forlin <[e-mail]>
Cc: Rabin Vincent <[e-mail]>
Acked-by: Vinod Koul <[e-mail]>
Signed-off-by: Lee Jones <[e-mail]>
Signed-off-by: Linus Walleij <[e-mail]>

drivers/dma/ste_dma40.c

···
 			       struct device_node *np)
 {
 	struct stedma40_platform_data *pdata;
-	int num_memcpy = 0;
+	int num_phy = 0, num_memcpy = 0;
 	const const __be32 *list;
 
 	pdata = devm_kzalloc(&pdev->dev,
···
 			     GFP_KERNEL);
 	if (!pdata)
 		return -ENOMEM;
+
+	/* If absent this value will be obtained from h/w. */
+	of_property_read_u32(np, "dma-channels", &num_phy);
+	if (num_phy > 0)
+		pdata->num_of_phy_chans = num_phy;
 
 	list = of_get_property(np, "memcpy-channels", &num_memcpy);
 	num_memcpy /= sizeof(*list);