nfp: fix copy paste in names and messages regarding vNICs

Data and control vNICs currently use the same area name and
error message.  This could lead to confusion.  Make sure
the error message says "ctrl" in case of control and the
data area is called "nfp.bar0".

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Simon Horman <simon.horman@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>