Disable more NVCC warnings.

The 2979 warning is yet another "calling a __host__ function from a
__host__ device__ function.  Although we probably should eventually
address these, they are flooding the logs.  Most of these are
harmless since we only call the original from the host.
In cases where these are actually called from device, an error is generated
instead anyways.

The 2977 warning is a bit strange - although the warning suggests the
`__device__` annotation is ignored, this doesn't actually seem to be
the case.  Without the `__device__` declarations, the kernel actually
fails to run when attempting to construct such objects.  Again,
these warnings are flooding the logs, so disabling for now.