drm/tiny: st7586: drop driver owner assignment

Core in spi_register_driver() already sets the .owner, so driver
does not need to.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: David Lechner <david@lechnology.com>
Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240327174842.519758-4-krzysztof.kozlowski@linaro.org