PCI: tegra: Add missing cleanup in error path and tegra_msi_teardown_irq()

We should call tegra_msi_free() to free the MSI bit if irq_create_mapping()
fails.  And we need to dispose the IRQ mapping during IRQ teardown.

[bhelgaas: made irqd_to_hwirq() change suggested by Thierry]
Signed-off-by: Jisheng Zhang <jszhang@marvell.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Thierry Reding <treding@nvidia.com>
Acked-by: Thierry Reding <treding@nvidia.com>