docs: i386: pc: Update maximum CPU numbers for PC Q35

Commit e4e98c7eebfa ("pc: q35: Bump max_cpus to 4096 vcpus") increases
the supported CPUs for PC Q35 machine.

Update maximum CPU numbers for PC Q35 in the document.

Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
Message-ID: <20240412085358.731560-1-zhao1.liu@linux.intel.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
diff --git a/docs/system/target-i386-desc.rst.inc b/docs/system/target-i386-desc.rst.inc
index 5ebbcda..319e540 100644
--- a/docs/system/target-i386-desc.rst.inc
+++ b/docs/system/target-i386-desc.rst.inc
@@ -36,7 +36,7 @@
 -  PCI UHCI, OHCI, EHCI or XHCI USB controller and a virtual USB-1.1
    hub.
 
-SMP is supported with up to 255 CPUs.
+SMP is supported with up to 255 CPUs (and 4096 CPUs for PC Q35 machine).
 
 QEMU uses the PC BIOS from the Seabios project and the Plex86/Bochs LGPL
 VGA BIOS.