amba: bus: balance firmware node reference counting

amba: bus: balance firmware node reference counting

Currently the ACPI code doesn't bump the reference count of
the firmware node, while OF counter part does. Not that it's
a problem right now, since ACPI doesn't really use the reference
counting for firmware nodes, it still makes sense to make code
robust against any changes done there. For this,
 - switch ACPI case to use device_set_node() to be unified with OF
 - move reference counting to amba_device_add()
 - switch to use firmware nodes instead of OF ones

In the result we will have reference counting done in the same module
for all callers independently on the nature of firmware node behind.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20231006145732.3419115-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Rob Herring <robh@kernel.org>