tools: ynl: process all scalar types encoding in single elif statement

As a preparation to handle enums for scalar values, unify the processing
of all scalar types in a single elif statement.

Signed-off-by: Jiri Pirko <jiri@nvidia.com>
Reviewed-by: Donald Hunter <donald.hunter@gmail.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Link: https://lore.kernel.org/r/20240222134351.224704-3-jiri@resnulli.us
Signed-off-by: Jakub Kicinski <kuba@kernel.org>