usb: xhci: Fix suspend/resume when used with OTG core

usb: xhci: Fix suspend/resume when used with OTG core

In the OTG case, the controller might not yet have been
added or is removed before the system suspends.

Assign xhci->main_hcd during probe to prevent NULL
pointer de-reference in xhci_suspend/resume().

Use the hcd->state flag to check if HCD is halted
and if that is so do nothing for xhci_suspend/resume().

[Only for xhci-plat devices, pci devices need it in gen_setup -Mathias]
Signed-off-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>