ARM: dts: iwg22d: Use /dev/ttySC3 as debug console

The BSP release from iWave uses /dev/ttySC3 as debug console, this patch
renames the alias accordingly for compatibility.

Signed-off-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
Signed-off-by: Chris Paterson <chris.paterson2@renesas.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>