usb: chipidea: udc: add the define TD_PAGE_COUNT and fix all users

A static count of transfer descriptors was used everywhere in the driver
with the fixed number 5. This patch adds a define, named TD_PAGE_COUNT,
and replaces all users of this value. This way its possible to have only
one parameter to change and limit the amount of buffer pointers per TD.

Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
Reviewed-by: Peter Chen <peter.chen@freescale.com>
Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>