spmi: pmic-arb: Register controller for bus instead of arbiter

Introduce the bus object in order to decouple the resources
that are bus specific from the arbiter. This way the SPMI controller
is registered with the generic framework at a bus level rather than
arbiter. This is needed in order to prepare for multi bus support.

Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Signed-off-by: Abel Vesa <abel.vesa@linaro.org>
Link: https://lore.kernel.org/r/20240417-spmi-multi-master-support-v10-6-5bc6d322e266@linaro.org
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Link: https://lore.kernel.org/r/53c31752-c8a2-4098-837e-2f84f03c8748@moroto.mountain
Signed-off-by: Stephen Boyd <sboyd@kernel.org>
Link: https://lore.kernel.org/r/20240507210809.3479953-12-sboyd@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: abelvesa