docs/vm: transhuge: split userspace bits to admin-guide/mm/transhuge

Now that the administrative information for transparent huge pages is
nicely separated, move it to its own page under the admin guide.
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/admin-guide/kernel-parameters.txt

@@ -4313,7 +4313,8 @@
 			Format: [always|madvise|never]
 			Can be used to control the default behavior of the system
 			with respect to transparent hugepages.
-			See Documentation/vm/transhuge.rst for more details.
+			See Documentation/admin-guide/mm/transhuge.rst
+			for more details.
 
 	tsc=		Disable clocksource stability checks for TSC.
 			Format: <string>

Documentation/admin-guide/mm/index.rst

@@ -27,4 +27,5 @@ the Linux memory management.
    numa_memory_policy
    pagemap
    soft-dirty
+   transhuge
    userfaultfd