net: wwan: t7xx: Fix the ACPI memory leak

The ACPI buffer memory (buffer.pointer) should be freed as the
buffer is not used after acpi_evaluate_object(), free it to
prevent memory leak.

Fixes: 13e920d9

 ("net: wwan: t7xx: Add core components")
Signed-off-by: Hanjun Guo <guohanjun@huawei.com>
Link: https://lore.kernel.org/r/1669119580-28977-1-git-send-email-guohanjun@huawei.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>