plat/common/efi: Add support for `TCG`'s `Reset Attack Mitigation`

plat/common/efi: Add support for `TCG`'s `Reset Attack Mitigation`

Add `Trusted Computing Group`'s `Reset Attack Mitigation` mechanism.
Whenever a machine shuts down or reboots, due to lack of electric
charge, the contents of RAM may dissipate after a short amount of
time. However this may be enough for an attacker to quickly boot
again into a custom program and dump memory contents. Thus, by using
this, the OS instructs POST BIOS to overwrite memory contents before
continuing to boot into the rest of the BIOS code.

Since this is not really implemented in `OVMF`'s `NVRAM` variables
we disable this by default.

Signed-off-by: Sergiu Moga <sergiu.moga@protonmail.com>
Reviewed-by: Michalis Pappas <michalis@unikraft.io>
Approved-by: Razvan Deaconescu <razvand@unikraft.io>
Tested-by: Unikraft CI <monkey@unikraft.io>
GitHub-Closes: #909