mlxsw: spectrum: Allow driver to load with old firmware versions

The driver fails to load with old firmware versions that cannot report
the maximum number of RIF MAC profiles [1].

Fix this by defaulting to a maximum of a single profile in such
situations, as multiple profiles are not supported by old firmware
versions.

[1]
mlxsw_spectrum 0000:03:00.0: cannot register bus device
mlxsw_spectrum: probe of 0000:03:00.0 failed with error -5

Fixes: 1c375ffb ("mlxsw: spectrum_router: Expose RIF MAC profiles to devlink resource")
Signed-off-by: Danielle Ratson <danieller@nvidia.com>
Reported-by: Vadim Pasternak <vadimp@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>