dmaengine: ioatdma: fix u16 overflow in reshape

If the allocation order is 16, then the u16 index will overflow and wrap
to zero instead of being equal or greater than 1 << 16.  The loop
condition will always be true, and the loop will run until all the
memory resources are depleted.

Change the type of index 'i' to u32, so that it is large enough to store
a value equal or greater than 1 << 16.

Signed-off-by: Allen Hubbe <Allen.Hubbe@emc.com>
Acked-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>