Your ofed.build.log points to a problem finding kernel source package for 3.8.0-34-generic.
The README for mlnx-ofed-kernel (see in MLNX_OFED_LINUX-2.0-3.0.0-ubuntu12.04-x86_64\SOURCES\mlnx-ofed-kernel_2.0.orig.tar.gz\mlnx-ofed-kernel-2.0) says that kernel subtree is based on kernel.org 3.7:
include/
drivers/
net/
Documentation/
So if kernel subtree for 3.8.0-34 differs from 3.7 it would explain why kernel source package cannot be found during build. Have you tried to use 3.7 kernel?
Also please share /var/lib/dkms/mlnx-ofed-kernel/2.0/build/make.log as it might have more details.
