arm64: dts: realtek: rtd129x: Fix GIC CPU masks for RTD1293

Convert from GIC_CPU_MASK_RAW() to GIC_CPU_MASK_SIMPLE().

In case of RTD1293 adjust the arch timer and VGIC interrupts'
CPU masks to its smaller number of CPUs.

Fixes: cf976f66 ("arm64: dts: realtek: Add RTD1293 and Synology DS418j")
Signed-off-by: Andreas Färber <afaerber@suse.de>