soundwire: validate DT compatible before parsing it

`sdw_of_find_slaves()` fetches raw `"compatible"` bytes with
`of_get_property()` and then immediately parses them with
`sscanf("sdw%01x%04hx%04hx%02hhx", ...)`.

Live-tree OF properties are stored as raw bytes plus a separate length;
they are not globally guaranteed to be NUL-terminated. Validate the
first compatible string before parsing it.

Signed-off-by: Pengpeng Hou <pengpeng@iscas.ac.cn>
Link: https://patch.msgid.link/20260403183504.4-soundwire-compatible-pengpeng@iscas.ac.cn
Signed-off-by: Vinod Koul <vkoul@kernel.org>

Author: neosys007

drivers/soundwire/slave.c

@@ -244,8 +244,8 @@ int sdw_of_find_slaves(struct sdw_bus *bus)
 		struct sdw_slave_id id;
 		const __be32 *addr;
 
-		compat = of_get_property(node, "compatible", NULL);
-		if (!compat)
+		ret = of_property_read_string(node, "compatible", &compat);
+		if (ret)
 			continue;
 
 		ret = sscanf(compat, "sdw%01x%04hx%04hx%02hhx", &sdw_version,