clk: fixed_rate: Avoid calling dev_read_*() if CONFIG_OF_PLATDATA=y

If CONFIG_OF_PLATDATA=y , then the udevice has no valid OF node associated
with it and ofnode_valid(node) evaluates to 0. The dev_read_u32_default()
call ultimately reaches ofnode_read_u32_index() which invokes fdt_getprop()
and passes result of ofnode_to_offset(node) as an offset parameter into it.

The ofnode_to_offset(node) returns -1 for invalid node, which leads to an
fdt_getprop(..., -1, ...) invocation, which will crash sandbox with SIGSEGV
because libfdt can not handle negative node offsets without full tree check,
which U-Boot inhibits to keep size lower.

Add dev_has_ofnode(dev) check and do not assign clock rate in case the
device has no valid node associated with it, and do not call any of the
dev_read_*() functions for devices without valid nodes.

Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>

drivers/clk/clk_fixed_rate.c

@@ -35,7 +35,7 @@ void clk_fixed_rate_ofdata_to_plat_(struct udevice *dev,
 				    struct clk_fixed_rate *plat)
 {
 	struct clk *clk = &plat->clk;
-	if (CONFIG_IS_ENABLED(OF_REAL))
+	if (dev_has_ofnode(dev))
 		plat->fixed_rate = dev_read_u32_default(dev, "clock-frequency",
 							0);