Kernel: Enable Write-Combine for FramebufferDevice

This enables much faster writing to the userspace mapped framebuffer,
if supported by the hardware.

Kernel/Graphics/FramebufferDevice.cpp

@@ -59,6 +59,8 @@ ErrorOr<Memory::Region*> FramebufferDevice::mmap(Process& process, OpenFileDescr
  "Framebuffer",
  prot,
  shared));
+ if (auto result = m_userspace_framebuffer_region->set_write_combine(true); result.is_error())
+ dbgln("FramebufferDevice: Failed to enable Write-Combine on Framebuffer: {}", result.error());
  return m_userspace_framebuffer_region;
 }