Extend existing driver for Spectrum, Spectrum-2 and Spectrum-3 ASICs
to support Spectrum-4 ASIC as well.

Currently there is no released firmware version for Spectrum-4, so the
driver is not enforcing a minimum version.
Signed-off-by: Amit Cohen <amcohen@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>