LU-11553 build: add download 7.5alternate for MOFED

LU-11553 build: add download 7.5alternate for MOFED

Mellanox download file name for aarch64 need to use
rhel7.5alternate as distro

Rename target file to be more precise which minor version
we are using

Change-Id: I02a31afa2a7803b3e78d975829a36a97eb64f021
Signed-off-by: Minh Diep <mdiep@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/33527
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Nathaniel Clark <nclark@whamcloud.com>
Reviewed-by: Jian Yu <yujian@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>