usb: xhci: remove duplicate code of interval checking

Move duplicate code from xhci_queue_intr_tx()
and xhci_queue_isoc_tx_prepare() to the check_interval() function.

Signed-off-by: Alexandr Ivanov <alexandr.sky@gmail.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>