arm64: dts: h3ulcb: update header

This updates H3ULCB device tree header with official board name
Signed-off-by: Vladimir Barinov <vladimir.barinov@cogentembedded.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

arch/arm64/boot/dts/renesas/r8a7795-h3ulcb.dts

 /*
- * Device Tree Source for the H3ULCB board
+ * Device Tree Source for the H3ULCB (R-Car Starter Kit Premier) board
  *
  * Copyright (C) 2016 Renesas Electronics Corp.
  * Copyright (C) 2016 Cogent Embedded, Inc.