This reverts commit 
602946ec2f90d5bd965857753880db29d2d9a1e9.
If CONFIG_HIGHMEM is enabled, no highmem will be added with max_mapnr
set to max_low_pfn, see mem_init():
  for (pfn = highmem_mapnr; pfn < max_mapnr; ++pfn) {
        ...
        free_highmem_page();
  }
Now that virt_addr_valid() has been fixed in the previous commit, we can
revert the change to max_mapnr.
Fixes: 602946ec2f90 ("powerpc: Set max_mapnr correctly")
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Reported-by: Erhard F. <erhard_f@mailbox.org>
[mpe: Update change log to reflect series reordering]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220406145802.538416-2-mpe@ellerman.id.au
 
 #endif
 
        high_memory = (void *) __va(max_low_pfn * PAGE_SIZE);
-       set_max_mapnr(max_low_pfn);
+       set_max_mapnr(max_pfn);
 
        kasan_late_init();