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

Fixes: 46b903a0 ("net, thunder, bgx: Add support to get MAC address from ACPI.")
Signed-off-by: Yu Liao <liaoyu15@huawei.com>
Link: https://lore.kernel.org/r/20221123082237.1220521-1-liaoyu15@huawei.comSigned-off-by: Paolo Abeni <pabeni@redhat.com>