nfp: only use kdoc style comments for kdoc

Update comments to only use kdoc style comments, starting with '/**',
for kdoc.

Flagged by ./scripts/kernel-doc

Signed-off-by: Simon Horman <simon.horman@corigine.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://lore.kernel.org/r/20220126090803.5582-1-simon.horman@corigine.com


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