tools: ynl-gen: use macro for binary min-len check

tools: ynl-gen: use macro for binary min-len check

This patch changes the generated min-len check for binary
attributes to use the NLA_POLICY_MIN_LEN() macro, thereby the
generated code supports strict policy validation.

With this change TypeBinary will always generate a NLA_BINARY
attribute policy.

This doesn't change any currently generated code, as it isn't
used in any specs currently used for generating code.

Signed-off-by: Asbjørn Sloth Tønnesen <ast@fiberby.net>
Reviewed-by: Donald Hunter <donald.hunter@gmail.com>
Link: https://patch.msgid.link/20250902154640.759815-3-ast@fiberby.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>