net/mlx5e: Rename lro_timeout to packet_merge_timeout

TIR stands for transport interface receive, the TIR object is
responsible for performing all transport related operations on
the receive side like packet processing, demultiplexing the packets
to different RQ's, etc.
lro_timeout is a field in the TIR that is used to set the timeout for lro
session, this series introduces new packet merge type, therefore rename
lro_timeout to packet_merge_timeout for all packet merge types.

Signed-off-by: Ben Ben-Ishay <benishay@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>