Logic fix for very high shadows on very large screens.
ON large screens like 5120x1440 calculated shadow map was 32768. That was 16x more than high setting, 32x more than medium setting and 64x more than low setting.

After this change shadow map sizes using very high setting by resolution will be following:
1920x1080 - 4096
2560x1440 - 4096
3840x1440 - 4096
5120x1440 - 8192
3840x2160 - 4096
7680x4320 - 8192
Patch by: @karmux
Reviewed by: @vladislavbelov, @Stan
Differential Revision: https://code.wildfiregames.com/D4723