I/OAT: fail initialization on zero channels detection

On some systems with I/OAT ver.2 when DCA is disabled in BIOS
situations have been observed
that zero DMA channels are detected instead of four.
To avoid kernel panic driver should fail gracefully with appropriate message.

Signed-off-by: Maciej Sosnowski <maciej.sosnowski@intel.com>
Signed-off-by: Shannon Nelson <shannon.nelson@intel.com>
Acked-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

diff --cc drivers/dma/ioat_dma.c
Simple merge