clk: keystone: syscon-clk: Do not use syscon helper to build regmap

clk: keystone: syscon-clk: Do not use syscon helper to build regmap

The syscon helper device_node_to_regmap() is used to fetch a regmap
registered to a device node. It also currently creates this regmap
if the node did not already have a regmap associated with it. This
should only be used on "syscon" nodes. This driver is not such a
device and instead uses device_node_to_regmap() on its own node as
a hacky way to create a regmap for itself.

This will not work going forward and so we should create our regmap
the normal way by defining our regmap_config, fetching our memory
resource, then using the normal regmap_init_mmio() function.

Signed-off-by: Andrew Davis <afd@ti.com>
Link: https://lore.kernel.org/r/20250123181913.597304-1-afd@ti.com
Tested-by: Nishanth Menon <nm@ti.com>
[sboyd@kernel.org: Drop dev_err_probe() because the mapping function
already does it]
Signed-off-by: Stephen Boyd <sboyd@kernel.org>