ACPI: Add common acpi_fill_gnvs()

Change-Id: I515e830808a95eee3ce72b16fd26da6ec79dac85
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/48718
Reviewed-by: Lance Zhao
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/include/acpi/acpi.h

@@ -961,6 +961,8 @@ void arch_fill_fadt(acpi_fadt_t *fadt);
 void soc_fill_fadt(acpi_fadt_t *fadt);
 void mainboard_fill_fadt(acpi_fadt_t *fadt);
 
+void acpi_fill_gnvs(void);
+
 void update_ssdt(void *ssdt);
 void update_ssdtx(void *ssdtx, int i);