netlink: specs: dpll: declare pad in the nests which carry 64-bit values

Pads need to be propagated to subsets if they are used.
Otherwise Python YNL can fail with:

  YnlException: Space 'frequency-range' has no attribute with value '4'

This affects only platforms which care about alignment
so not much real impact.

Reviewed-by: Ivan Vecera <ivecera@redhat.com>
Link: https://patch.msgid.link/20260924231211.568213-3-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/netlink/specs/dpll.yaml

@@ -550,6 +550,8 @@ attribute-sets:
     attributes:
       -
         name: parent-id
+      -
+        name: pad
       -
         name: direction
       -
@@ -576,6 +578,8 @@ attribute-sets:
     name: frequency-range
     subset-of: pin
     attributes:
+      -
+        name: pad
       -
         name: frequency-min
       -