net: thunderx: Fix the ACPI memory leak

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: 46b903a ("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.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

Author: yuliao0214

drivers/net/ethernet/cavium/thunder/thunder_bgx.c

@@ -1436,8 +1436,10 @@ static acpi_status bgx_acpi_match_id(acpi_handle handle, u32 lvl,
 		return AE_OK;
 	}
 
-	if (strncmp(string.pointer, bgx_sel, 4))
+	if (strncmp(string.pointer, bgx_sel, 4)) {
+		kfree(string.pointer);
 		return AE_OK;
+	}
 
 	acpi_walk_namespace(ACPI_TYPE_DEVICE, handle, 1,
 			    bgx_acpi_register_phy, NULL, bgx, NULL);