net/mlx5: Add init and destruction functions for a single HW clock

Move hardware clock initialization and destruction to the functions,
which will be used for dynamically allocated clock. Such clock is
shared by all the devices if the queried clock identities are same.

The out_work is for PPS out event, which can't be triggered when clock
is shared, so INIT_WORK is not moved to the initialization function.
Besides, we still need to register notifier for each device.

Signed-off-by: Jianbo Liu <jianbol@nvidia.com>
Reviewed-by: Carolina Jubran <cjubran@nvidia.com>
Reviewed-by: Dragos Tatulea <dtatulea@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>