mlxsw: core_env: Forbid module reset on RJ45 ports

Transceiver module reset through 'rst' field in PMAOS register is not
supported on RJ45 ports, so module reset should be rejected.

Therefore, before trying to access this field, validate the port module
type that was queried during initialization and return an error to user
space in case the port module type is RJ45 (twisted pair).

Output example:

 # ethtool --reset swp11 phy
 ETHTOOL_RESET 0x40
 Cannot issue ETHTOOL_RESET: Invalid argument
 $ dmesg
 mlxsw_spectrum 0000:03:00.0 swp11: Reset module is not supported on port module type

Signed-off-by: Danielle Ratson <danieller@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>