arm64: dts: h3ulcb: enable EXTALR clk

This enables EXTALR clock that can be used for the watchdog.

Signed-off-by: Vladimir Barinov <vladimir.barinov@cogentembedded.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>