soc/tegra: pmc: Remove genpd when adding provider fails

Commit 3fe57710 ("PM / Domains: Add support for removing PM
domains") add support for removing PM domains. Update the Tegra PMC
driver to remove PM domains if we fail to add a provider for the PM
domain.

Please note that the code under 'power_on_cleanup' label does not
really belong in the clean-up error path for tegra_powergate_add().
To keep the error path simple, remove this label and move the
associated code to where it needs to be invoked.

Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>