arm: tegra64: use unified boardfiles for fpga and silicon

arm: tegra64: use unified boardfiles for fpga and silicon

1. add grenada for dt_compat support.
2. remove tegra_fuse_calib_base_get_cp for t210 since
it's not implemented for t210.
3. don't initialize the clock table for fpga since it
don't need that.
4. build board-t210ref* for t210.

Change-Id: I2f4c56683947e2ecd1df4ad5c80f6709c8c7c44a
Signed-off-by: Kerwin Wan <kerwinw@nvidia.com>
Reviewed-on: http://git-master/r/456592
Reviewed-by: Bo Yan <byan@nvidia.com>