firmware/pmdomain: xilinx: Move ->sync_state() support to firmware driver

firmware/pmdomain: xilinx: Move ->sync_state() support to firmware driver

Rather than having the genpd provider to add device_links for each device
that gets attached, to implement the ->sync_state() support, let's rely on
fw_devlink to do this for us.

In this way, we can simplify the code by moving the ->sync_state() callback
into the firmware driver, so let's do that.

Cc: Michael Tretter <m.tretter@pengutronix.de>
Cc: Michal Simek <michal.simek@amd.com>
Tested-by: Hiago De Franco <hiago.franco@toradex.com> # Colibri iMX8X
Tested-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com> # TI AM62A,Xilinx ZynqMP ZCU106
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Link: https://lore.kernel.org/r/20250701114733.636510-15-ulf.hansson@linaro.org