powerpc: Don't flush caches when adding memory

This operation takes a significant amount of time when hotplugging
large amounts of memory (~50 seconds with 890GB of persistent memory).

This was orignally in commit fb5924f
("powerpc/mm: Flush cache on memory hot(un)plug") to support memtrace,
but the flush on add is not needed as it is flushed on remove.

Signed-off-by: Alastair D'Silva <[email protected]>
Signed-off-by: Michael Ellerman <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: deece

arch/powerpc/mm/mem.c

@@ -142,8 +142,6 @@ int __ref arch_add_memory(int nid, u64 start, u64 size,
 		return -EFAULT;
 	}
 
-	flush_dcache_range_chunked(start, start + size, FLUSH_CHUNK_SIZE);
-
 	return __add_pages(nid, start_pfn, nr_pages, restrictions);
 }