bus: ti-sysc: Fix handling of invalid clocks

We can currently get "Unable to handle kernel paging request at
virtual address" for invalid clocks with dts node but no driver:

(__clk_get_hw) from [<c0138ebc>] (ti_sysc_find_one_clockdomain+0x18/0x34)
(ti_sysc_find_one_clockdomain) from [<c0138f0c>] (ti_sysc_clkdm_init+0x34/0xdc)
(ti_sysc_clkdm_init) from [<c0584660>] (sysc_probe+0xa50/0x10e8)
(sysc_probe) from [<c065c6ac>] (platform_drv_probe+0x58/0xa8)

Let's add IS_ERR checks to ti_sysc_clkdm_init() as And let's start treating
clk_get() with -ENOENT as a proper error. If the clock name is specified
in device tree we must succeed with clk_get() to continue. For modules with
no clock names specified in device tree we will just ignore the clocks.

Fixes: 2b2f7def058a ("bus: ti-sysc: Add support for missing clockdomain handling")
Acked-by: Roger Quadros <rogerq@ti.com>
Tested-by: Keerthy <j-keerthy@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>
diff --git a/drivers/bus/ti-sysc.c b/drivers/bus/ti-sysc.c
index da88de4..24583d8 100644
--- a/drivers/bus/ti-sysc.c
+++ b/drivers/bus/ti-sysc.c
@@ -280,9 +280,6 @@ static int sysc_get_one_clock(struct sysc *ddata, const char *name)
 
 	ddata->clocks[index] = devm_clk_get(ddata->dev, name);
 	if (IS_ERR(ddata->clocks[index])) {
-		if (PTR_ERR(ddata->clocks[index]) == -ENOENT)
-			return 0;
-
 		dev_err(ddata->dev, "clock get error for %s: %li\n",
 			name, PTR_ERR(ddata->clocks[index]));
 
@@ -357,7 +354,7 @@ static int sysc_get_clocks(struct sysc *ddata)
 			continue;
 
 		error = sysc_get_one_clock(ddata, name);
-		if (error && error != -ENOENT)
+		if (error)
 			return error;
 	}