mlxsw: core_thermal: Rename labels according to naming convention

Rename labels for error flow handling in order to align with naming
convention used in rest of 'mlxsw' code.

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>