msm: pcie: add additional latency for PCIe switch case

Add the latency PCIe endpoint required before PCI framework scans
bus, when PCIe switch exists.

Change-Id: Ia567ccc217e7060c113b318c1bfb87e36b68cd93
Signed-off-by: Yan He <yanhe@codeaurora.org>
Signed-off-by: Tony Truong <truong@codeaurora.org>