nfp: fix readq on absolute RTsyms

Return the error and report value through the output param.

Fixes: 640917dd ("nfp: support access to absolute RTsyms")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Francois H. Theron <francois.theron@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>