platform/x86: mxm-wmi: fix memleak in mxm_wmi_call_mx[ds|mx]()

The ACPI buffer memory (out.pointer) returned by wmi_evaluate_method()
is not freed after the call, so it leads to memory leak.

The method results in ACPI buffer is not used, so just pass NULL to
wmi_evaluate_method() which fixes the memory leak.

Fixes: 99b38b4acc0d ("platform/x86: add MXM WMI driver.")
Signed-off-by: Yu Liao <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Reviewed-by: Hans de Goede <[e-mail]>
Signed-off-by: Hans de Goede <[e-mail]>

drivers/platform/x86/mxm-wmi.c

···
 		.xarg = 1,
 	};
 	struct acpi_buffer input = { (acpi_size)sizeof(args), &args };
-	struct acpi_buffer output = { ACPI_ALLOCATE_BUFFER, NULL };
 	acpi_status status;
 
 	printk("calling mux switch %d\n", adapter);
 
-	status = wmi_evaluate_method(MXM_WMMX_GUID, 0x0, adapter, &input,
-				     &output);
+	status = wmi_evaluate_method(MXM_WMMX_GUID, 0x0, adapter, &input, NULL);
 
 	if (ACPI_FAILURE(status))
 		return status;
···
 		.xarg = 1,
 	};
 	struct acpi_buffer input = { (acpi_size)sizeof(args), &args };
-	struct acpi_buffer output = { ACPI_ALLOCATE_BUFFER, NULL };
 	acpi_status status;
 
 	printk("calling mux switch %d\n", adapter);
 
-	status = wmi_evaluate_method(MXM_WMMX_GUID, 0x0, adapter, &input,
-				     &output);
+	status = wmi_evaluate_method(MXM_WMMX_GUID, 0x0, adapter, &input, NULL);
 
 	if (ACPI_FAILURE(status))
 		return status;