tools: ynl: use operation names from spec on the CLI

When I wrote the first version of the Python code I was quite
excited that we can generate class methods directly from the
spec. Unfortunately we need to use valid identifiers for method
names (specifically no dashes are allowed). Don't reuse those
names on the CLI, it's much more natural to use the operation
names exactly as listed in the spec.

Instead of:
  ./cli --do rings_get
use:
  ./cli --do rings-get

Signed-off-by: Jakub Kicinski <kuba@kernel.org>