As you may know Intel® graphics do not have dedicated memory but utilizes some of the computer's system memory. The amount of memory used for graphics may be a fixed amount or may vary up to a maximum amount. It depends on if your computer manufacturer has configured your computer to use a fixed amount, a dynamic amount (varying up to a maximum amount), or a combination of both fixed and dynamic amounts of graphics memory.
More information on this is available here:
In this case if you would like to address more memory to the video controller you will need to check with your computer manufacturer or motherboard manufacturer directly in order to check if this is possible for your system.