usb: drivers: Do not fragment IN transfers for Nordic.

Nordic device driver controller (usb_dc_nrfx.c) was fragmenting
IN transfers longer than wMaxPacketSize long using its
internal buffers. Buffers were reserved for each endpoint.
Because the Low level driver (nrfx) is capable of handling
fragmentation, there is no need to do it at the driver
controller level. Data pointer is used directly to create
the nrfx transfer. Endpoint buffers are not required anymore
and could be dropped.

This patch removes fragmentation of in transfers and omits
usage of internal endpoint buffers. Buffer could be later
freed by subsequent patches.

Nordic low level usbd driver is also capable of adding ZLP
if required however for consistance with the Zephyr USB device
stack ZLP must be triggered from stack level.

Signed-off-by: Emil Obalski <emil.obalski@nordicsemi.no>