mlxsw: core: Unify method of trap support validation

Currently there are several different features defined in 'mlxsw_driver'
for trap support validation. There is no reason to have dedicated
features for specific traps. Perform validation of all of them by
testing feature 'MLXSW_BUS_F_TXRX'.

Remove trap capability validation from 'core_env.c' which is redundant
after validation has been added to mlxsw_core_trap_register().

Signed-off-by: Vadim Pasternak <vadimp@nvidia.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>