ARM: dts: gemini: Push down flash address/size cells

The platforms not defining any OF partions complain like
this:

../arch/arm/boot/dts/gemini.dtsi:19.25-28.5: Warning
 (avoid_unnecessary_addr_size): /soc/flash@30000000: unnecessary
 #address-cells/#size-cells without "ranges" or child "reg" property

Get rid of this by only defining the address-cells and
size-cells where it is actually used by OF partitions.

Link: https://lore.kernel.org/r/20221204190230.3345590-1-linus.walleij@linaro.org


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>