nx_packet_length not set in rm_netxduo_ether_receive_packet()

[hwmaier]

The rm_netxduo_ether_receive_packet() ISR in file ra\fsp\src\rm_netxduo_ether\rm_netxduo_ether.c did not set the nx_packet_length field and left it set a 0. Subsequent update in line 523:

                        p_nx_buffers[index]->nx_packet_length      -= (NX_ETHERNET_SIZE + padding);

subtracts from 0, resulting in an erroneous length value of 4294967280 which causes issues further upstream in NetXDuo's processing. The nx_packet_append_ptr is also affected.

This PR set the nx_packet_length value based on the received packet's length.

[jritchey-renesas]

Confirmed this is a bug. It does seem like NetX Duo will correctly update the nx_packet_length, and nx_packet_append_ptr fields in _nx_ip_packet_receive(), however, if any of these fields are used before they are updated, then this will cause problems.

[jritchey-renesas]

Closes #148