xhci: Remove debugging about toggling cycle bits.

The code for toggling the cycle bits when the ring wraps around has
worked for years.  The print statement alone is not enough to indicate
there's something wrong with that code.  Now that full transfer tracing
has been ripped out, the print statement or lack thereof won't help
without context of where the enqueue pointer is.

Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>