dt-bindings: arm,gic: Fix binding example for a virt-capable GIC

The joys of copy/paste: the example of a virtualization capable GIC
in the DT binding was wrong, and propagated to dozens of platforms.
By having a GICC region that is only 4kB (instead of 8kB), we
end-up not being able to access the GICC_DIR register which is on
the second page.

Oh well. Let's fix the source of the crap before tackling individual
offenders.

Acked-by: Tony Lindgren <tony@atomide.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>