kho: fix order calculation for kho_unpreserve_pages()

kho: fix order calculation for kho_unpreserve_pages()

Commit 91e74fa8b1bc ("kho: make sure preservations do not span multiple
NUMA nodes") made sure preservations from kho_preserve_pages() do not
span multiple NUMA nodes. If they do, the order is reduced and tried
again.

The same logic was not implemented for kho_unpreserve_pages(). This can
result in unpreserve calculating a different order than preserve, and
thus not actually unpreserving the pages.

Fix this by moving the order calculation logic to
__kho_preserve_pages_order() and use it from both preserve and
unpreserve paths.

Move __kho_unpreserve() down to avoid having a forward declaration. Its
users are further down in the file anyway. Also, it results in grouping
for all the page-level preservation and unpreservation functions. This
unfortunately makes the diff hard to read, but the main change in
__kho_unpreserve() is to call __kho_preserve_pages_order() instead of
open-coding the order calculation.

Fixes: 91e74fa8b1bc ("kho: make sure preservations do not span multiple NUMA nodes")
Cc: stable@vger.kernel.org
Signed-off-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Reviewed-by: Samiullah Khawaja <skhawaja@google.com>
Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Link: https://patch.msgid.link/20260519133332.2498092-1-pratyush@kernel.org
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>