PCI: Add generic quirk for increasing D3hot delay

Separate the D3 delay increase functionality out of quirk_radeon_pm() into
its own function so that it can be shared with other quirks, including the
AMD Ryzen XHCI quirk that will be introduced in a followup commit.

Tweak the function name and message to indicate more clearly that the delay
relates to a D3hot-to-D0 transition.

Link: https://lore.kernel.org/r/20191127053836.31624-1-drake@endlessm.com


Signed-off-by: Daniel Drake <drake@endlessm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>