mlxsw: i2c: Add support for system interrupt handling

Extend i2c bus driver with interrupt handler to support system specific
hotplug events, related to line card state change.

Provide system IRQ line for interrupt handler. IRQ line Id could be
provided through the platform data if available, or could be set to the
default value.

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: Petr Machata <petrm@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>