drm/tiny: ili9486: Enable driver module autoloading

SPI devices use the spi_device_id for module autoloading even on
systems using device tree.

Add the spi_device_id entry to enable autoloading for the 3.5inch RPi
Display (rpi-lcd-35 and piscreen).

Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Signed-off-by: Carlo Caione <ccaione@baylibre.com>
Reviewed-by: Kamlesh Gurudasani <kamlesh.gurudasani@gmail.com>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20221116-s905x_spi_ili9486-v4-1-f86b4463b9e4@baylibre.com