usb: Fix tusb6010 for DMA API

Commit 18eabe23 introduced
DMA buffer ownership. Fix tusb6010 accordingly. To compile,
also dummy musb_platform_save and restore functions need to
be added.

Also change the order of musb_read_fifo() to happen after
dma_cache_maint to have the DMA operations completed before
moving the remaining unaligned bytes with PIO. The DMA
access and PIO touch different areas of the FIFO, so this
change only makes the code a bit easier to follow.

Tested on n810 and g_ether with variable size ping test.
The test seems to fail for some ping sizes, but that seems to
be a different problem.

Signed-off-by: Tony Lindgren <tony@atomide.com>
Acked-by: Felipe Balbi <felipe.balbi@nokia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>