arm64: dts: r8a7795: Drop 0x from unit address of gic

Drop 0x from unit address of gic as this is the desired form for
a unit address.

Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
Acked-by: Geert Uytterhoeven <geert+renesas@glider.be>