arm64: dts: renesas: r8a779g0: Add missing hypervisor virtual timer IRQ

Add the missing fifth interrupt to the device node that represents the
ARM architected timer.  While at it, add an interrupt-names property for
clarity,

Fixes: 987da486 ("arm64: dts: renesas: Add Renesas R8A779G0 SoC support")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/5eeabbeaea1c5fd518a608f2e8013d260b00fd7e.1718890849.git.geert+renesas@glider.be