ACPI/IORT: Fix iort_get_platform_device_domain() uninitialized pointer value

Running the Clang static analyzer on IORT code detected the following
error:

Logic error: Branch condition evaluates to a garbage value

in

iort_get_platform_device_domain()

If the named component associated with a given device has no IORT
mappings, iort_get_platform_device_domain() exits its MSI mapping loop
with msi_parent pointer containing garbage, which can lead to erroneous
code path execution.

Initialize the msi_parent pointer, fixing the bug.

Fixes: d4f54a186667 ("ACPI: platform: setup MSI domain for ACPI based
platform device")
Reported-by: Patrick Bellasi <patrick.bellasi@arm.com>
Reviewed-by: Hanjun Guo <hanjun.guo@linaro.org>
Acked-by: Will Deacon <will.deacon@arm.com>
Cc: Sudeep Holla <sudeep.holla@arm.com>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

drivers/acpi/arm64/iort.c

@@ -700,7 +700,7 @@ static void iort_set_device_domain(struct device *dev,
  */
 static struct irq_domain *iort_get_platform_device_domain(struct device *dev)
 {
-	struct acpi_iort_node *node, *msi_parent;
+	struct acpi_iort_node *node, *msi_parent = NULL;
 	struct fwnode_handle *iort_fwnode;
 	struct acpi_iort_its_group *its;
 	int i;