hw/arm/virt: Drop #size-cells and #address-cells from gpio-keys dtb node

hw/arm/virt: Drop #size-cells and #address-cells from gpio-keys dtb node

The virt board generates a gpio-keys node in the dtb, but it
incorrectly gives this node #size-cells and #address-cells
properties. If you dump the dtb with 'machine dumpdtb=file.dtb'
and run it through dtc, dtc will warn about this:

Warning (avoid_unnecessary_addr_size): /gpio-keys: unnecessary #address-cells/#size-cells without "ranges" or child "reg" property

Remove the bogus properties.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20220513131316.4081539-3-peter.maydell@linaro.org