dts: arm: renesas: Add ULPT and power state nodes for Renesas RA8

ULPT nodes:
- Added `ulpt0` at 0x40220000 (channel 0).
- Added `ulpt1` at 0x40220100 (channel 1).
- Included timer sub-nodes with `renesas,ra-ulpt-timer` compatibility.

Power state nodes:
- `stop0`: Runtime idle state mapped to LPM sleep mode.
- `stop1`: Standby state mapped to LPM software standby mode.

Signed-off-by: Khanh Nguyen <khanh.nguyen.wz@bp.renesas.com>