arm64: dts: renesas: r8a7796: Enable IPMMU devices

Remove 'status = "disabled"' to make sure all IPMMU devices are enabled
in DT on the r8a7796 SoC.

Signed-off-by: Magnus Damm <damm+renesas@opensource.se>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>