mlxsw: spectrum_mr_tcam: Push Spectrum-specific operations into a separate file

Since Spectrum-2 has different handling of TCAM, push Spectrum MR TCAM
bits to a separate file accessible by ops which allows to implement
Spectrum-2 specific ops.

Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>