Documentation: virt: correct location of haltpoll module params

Module parameters are located in sysfs, not debugfs, so correct the
statement.

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Link: https://lore.kernel.org/r/20230610054302.6223-1-rdunlap@infradead.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Author: rddunlap

Documentation/virt/guest-halt-polling.rst

@@ -72,7 +72,7 @@ high once achieves global guest_halt_poll_ns value).
 
 Default: Y
 
-The module parameters can be set from the debugfs files in::
+The module parameters can be set from the sysfs files in::
 
 	/sys/module/haltpoll/parameters/