backlight-tosa: Delete unnecessary assignment for the field "owner"

The field "owner" is set by the core.
Thus delete an unneeded initialisation.

Generated by: scripts/coccinelle/api/platform_no_drv_owner.cocci
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Lee Jones <lee.jones@linaro.org>