of/platform: Drop superfluous cast in of_device_make_bus_id()

There is no need to cast "u64" to "unsigned long long" before printing
it, as both types have been made identical on all architectures many
years ago.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Rob Herring <robh@kernel.org>