usb: mv_udc: Properly align the endpoint QH and qTD list

The endpoint QH list has to be aligned to 10-bit boundary. We also have
to make sure the list is aligned on a cacheline boundary. Make sure it
is. Furthermore, check if the memory allocation for the QH list didn't
fail. Moveover, improve the comment about the QH list structure.

Finally, the qTD item list has to be aligned only to 5-bit boundary, not
10-bit as it is now, fix this as well.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Fabio Estevam <fabio.estevam@freescale.com>
Cc: Lei Wen <leiwen@marvell.com>
Cc: Otavio Salvador <otavio@ossystems.com.br>
Cc: Stefano Babic <sbabic@denx.de>