Documentation: document liveupdate cmdline parameter

liveupdate is used to enable Live Update Orchestrator (LUO) early during
boot.  Add it to kernel-parameters.txt so users can discover and use it.

Link: https://lkml.kernel.org/r/20260130112036.359806-1-me@linux.beauty
Signed-off-by: Li Chen <me@linux.beauty>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: "Borislav Petkov (AMD)" <bp@alien8.de>
Cc: Frank van der Linden <fvdl@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kees Cook <kees@kernel.org>
Cc: Li RongQing <lirongqing@baidu.com>
Cc: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Pratyush Yadav <ptyadav@amazon.de>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: FirstLoveLife

Documentation/admin-guide/kernel-parameters.txt

@@ -3472,6 +3472,11 @@ Kernel parameters
 			If there are multiple matching configurations changing
 			the same attribute, the last one is used.
 
+	liveupdate=	[KNL,EARLY]
+			Format: <bool>
+			Enable Live Update Orchestrator (LUO).
+			Default: off.
+
 	load_ramdisk=	[RAM] [Deprecated]
 
 	lockd.nlm_grace_period=P  [NFS] Assign grace period.