firmware/tegra: Enable Tegra186 BPMP support on Tegra194

The BPMP implementation on Tegra194 is mostly compatible with the
implementation on Tegra186, so make sure the latter is available when
support for Tegra194 is enabled.

Suggested-by: Timo Alho <talho@nvidia.com>
Reviewed-by: Timo Alho <talho@nvidia.com>
Tested-by: Timo Alho <talho@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>