net: ethernet: ti: am65-cpsw-nuss: Fix port_id extraction from SRC TAG

In the Linux kernel, the following vulnerability has been resolved: net: ethernet: ti: am65-cpsw-nuss: Fix port_id extraction from SRC TAG On the packet reception path, the ID of the MAC Port on which the packet was received, is embedded in the RX DMA Descriptor's metadata. The ID is extracted using the helper function cppi5_desc_get_tags_ids() which fills in the 16-bit Source Tag into the 'port_id' variable. However, it is only the lower 8-bits of the 16-bit Source Tag that represent the MAC Port ID, while the upper 8-bits are Hardware-Reserved and carry an arbitrary value. With the existing logic, sporadic kernel crash is observed due to the subsequent driver code accessing out-of-bound memory because of an invalid port_id. Hence, fix the port_id extraction logic to use only the lower 8-bits of the Source Tag as the MAC Port ID.