stand/efi: Define ACPI_USE_SYSTEM_INTTYPES to be 1 instead of blank

To avoid a redefinition warning... This needs to be redone correctly,
but this gets amd64 building again... My amd64 environment is polluted
with something that caues earlier failures which I ignored...

Fixes: 488bc7e9a777
Sponsored by: Netflix

(cherry picked from commit e4789047ffd1319be337711ae4b6c594378f31b2)