drm/ssd130x: Set SPI .id_table to prevent an SPI core warning

drm/ssd130x: Set SPI .id_table to prevent an SPI core warning

The only reason for the ssd130x-spi driver to have an spi_device_id table
is that the SPI core always reports an "spi:" MODALIAS, even when the SPI
device has been registered via a Device Tree Blob.

Without spi_device_id table information in the module's metadata, module
autoloading would not work because there won't be an alias that matches
the MODALIAS reported by the SPI core.

This spi_device_id table is not needed for device matching though, since
the of_device_id table is always used in this case. For this reason, the
struct spi_driver .id_table member is currently not set in the SPI driver.

Because the spi_device_id table is always required for module autoloading,
the SPI core checks during driver registration that both an of_device_id
table and a spi_device_id table are present and that they contain the same
entries for all the SPI devices.

Not setting the .id_table member in the driver then confuses the core and
leads to the following warning when the ssd130x-spi driver is registered:

  [   41.091198] SPI driver ssd130x-spi has no spi_device_id for sinowealth,sh1106
  [   41.098614] SPI driver ssd130x-spi has no spi_device_id for solomon,ssd1305
  [   41.105862] SPI driver ssd130x-spi has no spi_device_id for solomon,ssd1306
  [   41.113062] SPI driver ssd130x-spi has no spi_device_id for solomon,ssd1307
  [   41.120247] SPI driver ssd130x-spi has no spi_device_id for solomon,ssd1309
  [   41.127449] SPI driver ssd130x-spi has no spi_device_id for solomon,ssd1322
  [   41.134627] SPI driver ssd130x-spi has no spi_device_id for solomon,ssd1325
  [   41.141784] SPI driver ssd130x-spi has no spi_device_id for solomon,ssd1327
  [   41.149021] SPI driver ssd130x-spi has no spi_device_id for solomon,ssd1331

To prevent the warning, set the .id_table even though it's not necessary.

Since the check is done even for built-in drivers, drop the condition to
only define the ID table when the driver is built as a module. Finally,
rename the variable to use the "_spi_id" convention used for ID tables.

Fixes: 74373977d2ca ("drm/solomon: Add SSD130x OLED displays SPI support")
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20241231114516.2063201-1-javierm@redhat.com
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>