mm/mm_init: fix hash table order logging in alloc_large_system_hash()

mm/mm_init: fix hash table order logging in alloc_large_system_hash()

When emitting the order of the allocation for a hash table,
alloc_large_system_hash() unconditionally subtracts PAGE_SHIFT from log
base 2 of the allocation size.  This is not correct if the allocation size
is smaller than a page, and yields a negative value for the order as seen
below:

TCP established hash table entries: 32 (order: -4, 256 bytes, linear) TCP
bind hash table entries: 32 (order: -2, 1024 bytes, linear)

Use get_order() to compute the order when emitting the hash table
information to correctly handle cases where the allocation size is smaller
than a page:

TCP established hash table entries: 32 (order: 0, 256 bytes, linear) TCP
bind hash table entries: 32 (order: 0, 1024 bytes, linear)

Link: https://lkml.kernel.org/r/20251028191020.413002-1-isaacmanjarres@google.com
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Isaac J. Manjarres <isaacmanjarres@google.com>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>