xhci: hack, delay clearing CSC connect status change flag until device is freed.

Some controllers might immediately suspend when last connected device is
disconnected and host driver clears the connect status chage flag (CSC)

Try to keep the host alive a bit longer to complete pending commands
by clearing the CSC bit  later.

Patch for testing only, not upstream

Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>