octeontx2-af: debugfs: delete dead code

These debugfs never return NULL so all this code will never be run.

In the normal case, (and in this case particularly), the debugfs
functions are not supposed to be checked for errors so all this error
checking code can be safely deleted.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/X8c6vpapJDYI2eWI@mwandaSigned-off-by: Jakub Kicinski <kuba@kernel.org>