tools/net/ynl: add indexed-array scalar support to ynl-gen-c

Extend ynl-gen-c.py with support for indexed-array that has a scalar
sub-type.

Signed-off-by: Donald Hunter <donald.hunter@gmail.com>
Link: https://patch.msgid.link/20250211120127.84858-8-donald.hunter@gmail.com


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