nfp: fix incumbent kdoc warnings

We should use % instead of @ for documenting preprocessor defines.
Add missing documentation of __NFP_REPR_TYPE_MAX.  This gets rid
of all remaining kdoc warnings in the driver.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>