arm64: dts: renesas: r8a77995: Fix register range of display node

Since the R8A77995 SoC uses DU{0,1}, the range from the base address to
the 0x4000 address is used.
This patch fixed it.

Fixes: 18f1a773 ("arm64: dts: renesas: r8a77995: add DU support")
Signed-off-by: Yoshihiro Kaneko <ykaneko0929@gmail.com>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>