docs: Update console=pv requirement

PV console doesn't require Xen to be running as a shim and only
requires CONFIG_XEN_GUEST and running as a Xen guest. Update the
documentation accordingly.

Fixes: 4f6609d6a6 ("x86/guest: use PV console for Xen/Dom0 I/O")
Signed-off-by: Teddy Astie <teddy.astie@vates.tech>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
master commit: f47c2e96ab
master date: 2026-05-21 09:13:42 +0200

docs/misc/xen-command-line.pandoc

@@ -446,8 +446,9 @@ the converse; transmitted and received characters will have their MSB
 cleared.  This allows a single port to be shared by two subsystems
 (e.g. console and debugger).
 
-`pv` indicates that Xen should use Xen's PV console. This option is
-only available when used together with `pv-in-pvh`.
+`pv` indicates that Xen should use Xen's PV console. This option requires
+Xen running as a Xen guest. and is only available if the hypervisor was
+compiled with `CONFIG_XEN_GUEST` enabled.
 
 `dbgp` or `ehci` indicates that Xen should use a USB2 debug port.