xhci: unify cycle state toggling operation with 'XOR'

Some toggling operation in xHCI driver still use conditional toggling:
ring->cycle_state = (ring->cycle_state ? 0 : 1);

Use XOR to invert the cycle state instead of a conditional toggle to unify
cycle state toggling operation in xHCI driver.

Signed-off-by: Lin Wang <lin.x.wang@intel.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>