arm64: dts: renesas: r8a77965: Remove reg-names of display node

Remove the "reg-names" property from the display node of R-Car Gen3 R8A77965
device tree.

No other mainline R-Car Gen3 SoC has that property specified.

Fixes: 2f2c71bf ("arm64: dts: renesas: r8a77965: Populate the DU instance placeholder")

Signed-off-by: Takeshi Kihara <takeshi.kihara.df@renesas.com>
[reworded commit message, sent upstream]
Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>