drm/dp: Move from u16 to u32 for max in drm_edp_backlight_info

drm/dp: Move from u16 to u32 for max in drm_edp_backlight_info

Use u32 instead of u16 for max variable in drm_edp_backlight_info
since it can now hold max luminance range value which is u32.
We will set this max with max_luminance value when luminance_set is
true.

Signed-off-by: Suraj Kandpal <suraj.kandpal@intel.com>
Reviewed-by: Arun R Murthy <arun.r.murthy@intel.com>
Link: https://lore.kernel.org/r/20250620063445.3603086-5-suraj.kandpal@intel.com