usb: musb: use DMA mode 1 whenever possible

Do not rely on any hints from gadget drivers and use DMA mode 1
whenever we expect data of at least the endpoint's packet size and
have not yet received a short packet.

The last packet if short is always transferred using DMA mode 0.

This patch fixes USB throughput issues in mass storage mode for
host to device transfers.

Signed-off-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>