USB: musb cppi dma fix

Initializes the actual_len field to 0 before every DMA transaction.

Signed-off-by: Swaminathan S <swami.iyer@ti.com>
Acked-by: Felipe Balbi <felipe.balbi@nokia.com>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>