clk: ti: consider the fact that of_clk_get() might return an error

I "forgot" to update the dtb and the kernel crashed:
|Unable to handle kernel NULL pointer dereference at virtual address 0000002e
|PC is at __clk_get_flags+0x4/0xc
|LR is at ti_dt_clockdomains_setup+0x70/0xe8

because I did not have the clock nodes. of_clk_get() returns an error
pointer which is not checked here.
Acked-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Tero Kristo <t-kristo@ti.com>

drivers/clk/ti/clockdomain.c

@@ -36,6 +36,11 @@ static void __init of_ti_clockdomain_setup(struct device_node *node)
 
 	for (i = 0; i < num_clks; i++) {
 		clk = of_clk_get(node, i);
+		if (IS_ERR(clk)) {
+			pr_err("%s: Failed get %s' clock nr %d (%ld)\n",
+			       __func__, node->full_name, i, PTR_ERR(clk));
+			continue;
+		}
 		if (__clk_get_flags(clk) & CLK_IS_BASIC) {
 			pr_warn("can't setup clkdm for basic clk %s\n",
 				__clk_get_name(clk));