ioat2: kill pending flag

The pending == 2 case no longer exists in the driver so, we can use
ioat2_ring_pending() outside the lock to determine if there might be any
descriptors in the ring that the hardware has not seen.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>

diff --cc drivers/dma/ioat/dma_v2.c
Simple merge

diff --cc drivers/dma/ioat/dma_v2.h
Simple merge