mlxsw: core_env: Defer handling of module temperature warning events

Module temperature events are currently handled in softIRQ context,
requiring the 'module_info_lock' to be a spin lock. In future patchsets
we will need to be able to hold the lock while sleeping.

Therefore, defer handling of these events using a work queue so that the
next patch will be able to convert the lock to a mutex.

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