[RFC PATCH] powerpc: fix get_arch_dma_ops() for NTB devices

get_dma_ops() falls into arch-dependant get_arch_dma_ops(), which historically returns NULL on PowerPC. Therefore dma_set_mask() fails. This affects Switchtec (and probably other) NTB devices, that they fail to initialize. The proposed patch should fix the issue. ---

Unexpectedly dma_ops is NULL in struct device

Hello, I tried to use Switchtec NTB on PowerPC platform and faced a strange behaviour. In ntb_hw_switchtec module's initialization section the "struct device" has uninitialized field dma_ops (NULL). Meanwhile the same NTB hardware on x86 platform get correct dma_ops in this driver. It looks