docs/man: Add altp2m_count parameter to the xl.cfg manual

Update manual pages to include detailed information about the altp2m_count
configuration parameter.

Signed-off-by: Petr Beneš <w1benny@gmail.com>
Acked-by: Anthony PERARD <anthony.perard@vates.tech>

docs/man/xl.cfg.5.pod.in

@@ -2023,6 +2023,20 @@ a single guest HVM domain. B<This option is deprecated, use the option
 B<Note>: While the option "altp2mhvm" is deprecated, legacy applications for
 x86 systems will continue to work using it.
 
+=item B<altp2m_count=NUMBER>
+
+Specifies the maximum number of alternate-p2m views available to the guest.
+This setting is crucial in domain introspection scenarios that require
+multiple physical-to-machine (p2m) memory mappings to be established
+simultaneously.
+
+Enabling multiple p2m views may increase memory usage. It is advisable to
+review and adjust the B<shadow_memory> setting as necessary to accommodate
+the additional memory requirements.
+
+B<Note>: This option is ignored if B<altp2m> is disabled. The default value
+is 10.
+
 =item B<nestedhvm=BOOLEAN>
 
 Enable or disables guest access to hardware virtualisation features,