doc: update params of memhp_default_state=

Commit 5f47adf7 ("mm/memory_hotplug: allow to specify a default
online_type") allows to specify a default online_type which make
online memory to kernel or movable zone possible but fail to update
to doc. Update doc to fit this change.
Signed-off-by: Ma Wupeng <mawupeng1@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20230802074312.2111074-1-mawupeng1@huawei.com

Documentation/admin-guide/kernel-parameters.txt

@@ -3105,7 +3105,7 @@
 			[KNL,SH] Allow user to override the default size for
 			per-device physically contiguous DMA buffers.
 
-	memhp_default_state=online/offline
+	memhp_default_state=online/offline/online_kernel/online_movable
 			[KNL] Set the initial state for the memory hotplug
 			onlining policy. If not specified, the default value is
 			set according to the