platform/x86: alienware-wmi: Correct a memory leak

commit ff0e9f26288d2daee4950f42b37a3d3d30d36ec1 upstream.

An ACPI buffer that was allocated was not being freed after use.

Signed-off-by: Mario Limonciello <mario.limonciello@dell.com>
Cc: stable@vger.kernel.org
Signed-off-by: Darren Hart (VMware) <dvhart@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>