nfp: remove automatic caching of RTsym table

The fact that RTsym table is cached inside nfp_cpp handle is
a relic of old times when nfpcore was a library module.  All
the nfp_cpp "caches" are awkward to deal with because of
concurrency and prone to keeping stale information.  Make
the run time symbol table be an object read out from the device
and managed by whoever requested it.  Since the driver loads
FW at ->probe() and never reloads, we can hold onto the table
for ever.

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