usb: mv_udc: Add proper cache management

Implement functions to flush/invalidate dcache over QH and qTDs
and make use of them where appropriate. Also use them to replace
the old incorrect cache management attempt. This is the first step
towards making this driver work with data cache enabled.

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>