drivers/wifi/generic/acpi.c: NULL-check pointers before dereferencing

Checking whether a pointer is NULL after it has been dereferenced makes
zero sense. Make sure the `wifi_ssdt_write_properties()` function never
gets invoked with a NULL argument for the `dev` parameter, and simplify
the logic around the `is_cnvi_ddr_rfim_enabled` variable accordingly.

Change-Id: I3fbc9565e7e9b4e1c14a68f6a5fd779577045236
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/63340
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Felix Singer <felixsinger@posteo.net>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
diff --git a/src/drivers/wifi/generic/acpi.c b/src/drivers/wifi/generic/acpi.c
index 65940d6..ee09631 100644
--- a/src/drivers/wifi/generic/acpi.c
+++ b/src/drivers/wifi/generic/acpi.c
@@ -533,11 +533,9 @@
 
 static void wifi_ssdt_write_properties(const struct device *dev, const char *scope)
 {
-	bool is_cnvi_ddr_rfim_enabled = false;
-
 	const struct drivers_wifi_generic_config *config = dev->chip_info;
-	if (dev && config)
-		is_cnvi_ddr_rfim_enabled = config->enable_cnvi_ddr_rfim;
+
+	bool is_cnvi_ddr_rfim_enabled = config && config->enable_cnvi_ddr_rfim;
 
 	/* Scope */
 	acpigen_write_scope(scope);
@@ -646,6 +644,8 @@
 void wifi_cnvi_fill_ssdt(const struct device *dev)
 {
 	const char *path;
+	if (!dev)
+		return;
 
 	path = acpi_device_path(dev->bus->dev);
 	if (!path)