firmware: arm_scmi: Fix uninitialized pointers with __free attr

Uninitialized pointers with `__free` attribute can cause undefined
behaviour as the memory assigned(randomly) to the pointer is freed
automatically when the pointer goes out of scope

arm doesn't have any bugs related to this as of now, but
it is better to initialize and assign pointers with `__free` attr
in one statement to ensure proper scope-based cleanup

Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/all/aPiG_F5EBQUjZqsl@stanley.mountain/
Signed-off-by: Ally Heev <allyheev@gmail.com>
Reviewed-by: Cristian Marussi <cristian.marussi@arm.com>
Message-Id: <20251105-aheev-uninitialized-free-attr-arm-v1-1-f7b6cb5d3361@gmail.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

Author: aheev

drivers/firmware/arm_scmi/shmem.c

@@ -196,7 +196,6 @@ static void __iomem *shmem_setup_iomap(struct scmi_chan_info *cinfo,
 				       struct resource *res,
 				       struct scmi_shmem_io_ops **ops)
 {
-	struct device_node *shmem __free(device_node);
 	const char *desc = tx ? "Tx" : "Rx";
 	int ret, idx = tx ? 0 : 1;
 	struct device *cdev = cinfo->dev;
@@ -205,7 +204,9 @@ static void __iomem *shmem_setup_iomap(struct scmi_chan_info *cinfo,
 	void __iomem *addr;
 	u32 reg_io_width;
 
-	shmem = of_parse_phandle(cdev->of_node, "shmem", idx);
+	struct device_node *shmem __free(device_node) = of_parse_phandle(cdev->of_node,
+		"shmem", idx);
+
 	if (!shmem)
 		return IOMEM_ERR_PTR(-ENODEV);