cnss: Set D3hot state only after saving config space

CNSS saves the PCIe config space but that is done after entering
D3hot state. In D3hot, PCIe endpoint would be aggressive to go to
low power mode. Because of this saving and restoring config space
may take longer time. With this change, about 5 times improvement
is seen while saving/restoring the config space.

Change-Id: I847e8efeab7b0ce5b4ddcec367997ae14373900d
Signed-off-by: Prashanth Bhatta <bhattap@codeaurora.org>