boards: renesas: Correct the spi node on ek_ra8d1

Currently, the SPI pinctrl is incorrect for the spi0 node.
In this PR (#77850), we changed the pinctrl number for SPI
from spi0 to spi1, but we forgot to update the node name
to spi1.
This commit aims to fix:
- Correct the pinctrl name for spi
- Correct the spi node on ek_ra8d1.dts

Signed-off-by: Khoa Nguyen <khoa.nguyen.xh@renesas.com>