powerpc/powernv: remove unused NPU DMA code

None of these routines were ever used anywhere in the kernel tree
since they were added to the kernel.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/mm/book3s64/mmu_context.c

@@ -179,7 +179,6 @@ static int radix__init_new_context(struct mm_struct *mm)
 	 */
 	asm volatile("ptesync;isync" : : : "memory");
 
-	mm->context.npu_context = NULL;
 	mm->context.hash_context = NULL;
 
 	return index;