net: thunderx: Rewrite silicon revision tests.

The test for pass-1 silicon was incorrect, it should be for all
revisions less than 8.  Also the revision is already present in the
pci_dev, so there is no need to read and keep a private copy.

Remove rev_id and code to read it from struct nicpf.  Create new
static inline function pass1_silicon() to be used to testing the
silicon version.  Use pass1_silicon() for revision checks, this will
be more widely used in follow on patches.

Signed-off-by: David Daney <david.daney@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>