RHEL_Dockerfile default D_OFED_URL_PATH no longer works with DOCA 3.1.0

[tginer]

For previous DOCA versions, such as v2.9, the D_OFED_URL_PATH parameter was successfully built as:

D_OFED_BASE_URL="https://linux.mellanox.com/public/repo/doca/${D_DOCA_VERSION}/SOURCES/MLNX_OFED"

But this is no longer working for DOCA 3.1.0, due to the mlnx_ofed/ folder name change from MLNX_OFED to mlnx_ofed:

https://linux.mellanox.com/public/repo/doca/3.1.0/SOURCES/mlnx_ofed/