soc: brcmstb: Only register SoC device on STB platforms

After moving the SoC device initialization to an early initcall in
commit f780429a ("soc: brcmstb: biuctrl: Move to early_initcall"),
the Broadcom STB SoC device is registered on all platforms if support
for the device is enabled in the kernel configuration.

This causes an additional SoC device to appear on platforms that already
register a native one. In case of Tegra the STB SoC device is registered
as soc0 (with totally meaningless content in the sysfs attributes) and
causes various scripts and programs to fail because they don't know how
to parse that data.

To fix this, duplicate the check from brcmstb_soc_device_early_init()
that already prevents the code from doing anything nonsensical on non-
STB platforms.

Fixes: f780429a ("soc: brcmstb: biuctrl: Move to early_initcall")
Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Olof Johansson <olof@lixom.net>

drivers/soc/bcm/brcmstb/common.c

@@ -89,8 +89,13 @@ early_initcall(brcmstb_soc_device_early_init);
 static int __init brcmstb_soc_device_init(void)
 {
 	struct soc_device_attribute *soc_dev_attr;
+	struct device_node *sun_top_ctrl;
 	struct soc_device *soc_dev;
 
+	sun_top_ctrl = of_find_matching_node(NULL, sun_top_ctrl_match);
+	if (!sun_top_ctrl)
+		return -ENODEV;
+
 	soc_dev_attr = kzalloc(sizeof(*soc_dev_attr), GFP_KERNEL);
 	if (!soc_dev_attr)
 		return -ENOMEM;