usb: xhci: Cleanup printk debug message for ERST

Each event segment has been exposed through debugfs. There is no
need to dump ERST content with printk in code. Remove it to make
code more concise and readable.

Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>