carl9170 firmware: Initialize USB subsystem before the DMA engine

The documentation states that the USB DMA engine control register
(0x1e1108) should be modified when the state engine is idling.
By tuning the initialization order and placing a larger workload
in between, the state machine should now always be in the correct
state.

Signed-off-by: Christian Lamparter <chunkeey@googlemail.com>