pmdomain: thead: Instantiate GPU power sequencer via auxiliary bus

pmdomain: thead: Instantiate GPU power sequencer via auxiliary bus

In order to support the complex power sequencing required by the TH1520
GPU, the AON power domain driver must be responsible for initiating the
corresponding sequencer driver. This functionality is specific to
platforms where the GPU power sequencing hardware is controlled by the
AON block.

Extend the AON power domain driver to check for the presence of the
"gpu-clkgen" reset in its own device tree node.

If the property is found, create and register a new auxiliary device.
This device acts as a proxy that allows the dedicated `pwrseq-thead-gpu`
auxiliary driver to bind and take control of the sequencing logic.

Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Reviewed-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Signed-off-by: Michal Wilczynski <m.wilczynski@samsung.com>
Link: https://lore.kernel.org/r/20250623-apr_14_for_sending-v6-3-6583ce0f6c25@samsung.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>