PCI: tegra: Fix PLLE power down issue due to CLKREQ# signal

Disable controllers which failed to bring the link up and configure
CLKREQ# signals of these controllers as GPIO. This is required to avoid
CLKREQ# signal of inactive controllers interfering with PLLE power down
sequence.

PCIE_CLKREQ_GPIO bits are defined only in Tegra186, however programming
these bits in other SoCs doesn't cause any side effects. Program these
bits for all Tegra SoCs to avoid a conditional check.

Signed-off-by: Manikanta Maddireddy <mmaddireddy@nvidia.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: Thierry Reding <treding@nvidia.com>