mlxsw: spectrum_ethtool: Remove internal speeds from PTYS register

The PTYS register is used to report and configure the port type and
speed. Currently, internal bits in the register are used the same way
other bits are used.

Using the internal bits can cause bad parameter firmware errors. For
example, trying to write to internal bit 25 returns:

EMAD reg access failed (tid=53e2bffa00004310,reg_id=5004(ptys),type=write,status=7(bad parameter))

Remove the internal bits from the PTYS register, so that it is no longer
possible to pass them to firmware.

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