tools: ynl-gen: support uint in multi-attr

The ethtool FEC histogram series run into a build issue with
type: uint + multi-attr: True. Auto scalars use 64b types,
we need to convert them explicitly when rendering the types.

No current spec needs this, and the ethtool FEC histogram
doesn't need this either any more, so not posting as a fix.

Link: https://lore.kernel.org/8f52c5b8-bd8a-44b8-812c-4f30d50f63ff@redhat.com


Reviewed-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
Reviewed-by: Donald Hunter <donald.hunter@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>