usb: host: Fix unclocked access in xhci_suspend in case of pm suspend

When runtime suspend occurs xhci_suspend is called and now all the
clocks are turned off. Now if pm_suspend happens xhci_suspend is again
called which leads to unclocked access of registers in function
xhci_disable_hub_port_wake. Fix this by considering second
call of xhci_suspend due to pm_suspend as no-op.

Change-Id: Ic053636ac1d6c54150b40e5477b5eb373fcdbeb3
Signed-off-by: Rohith Kollalsi <quic_rkollals@quicinc.com>