nfp: add support for service processor access

NFP Service Processor (NSP) is an ARM core inside the chip which
is responsible for management and control functions.  Add support
for chip reset, FW load and external module access using the NSP.

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