drm/panel: ld9040: reference spi_device_id table

Reference the spi_device_id table to silence W=1 warning:

  drivers/gpu/drm/panel/panel-samsung-ld9040.c:377:35:
    warning: ‘ld9040_ids’ defined but not used [-Wunused-const-variable=]

This also would be needed for matching the driver if booted without
CONFIG_OF (although it's not necessarily real case).

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210526123002.12913-1-krzysztof.kozlowski@canonical.com