Minimial Changes for MSI Z790P DDR4 dCPU Support

[mdrobnak]

• Update Linux config to add PROC_SYSCTL. Got errors on boot from Heads about this missing
• Add new board config msi_z790p_ddr4_dgpu with corresponding coreboot config
• Runs VGA Option ROM
• Qubes prompts for Disk Unlock in graphics mode
• Ubuntu works fine
• Can switch in and out of X VT without issues

Variations Tested:

• VGA Text Mode, Native Execution. This PR
• VGA Text Mode, Secure Execution. NVidia causes 4 beeps and no progress. AMD successful.
• VESA Framebuffer mode. NVidia causes 4 beeps and no progress. AMD ignores, which causes Disk Unlock to be in odd state with Qubes (ASCII Art-style progress bar that falls back to text prompt for password).
• Load GOP - Black screen. Same for both NVidia and AMD.

CONFIG_USB_KEYBOARD does not seem to be the correct configuration item. Updated PR with CONFIG_SUPPORT_USB_KEYBOARD and turning it on by default using CONFIG_USER_USB_KEYBOARD.

[miczyg1]

@macpijan I can bring my AMD GPU to test this PR on Thursday. Although I would need the boards to be functional in our lab. Last time I tried, the board were not flashing using osfv_cli