ACPI: Refactor ChromeOS specific ACPI GNVS

The layout of GNVS has expectation for a fixed size
array for chromeos_acpi_t. This allows us to reduce
the exposure of <chromeos/gnvs.h>.

If chromeos_acpi_t was the last entry in struct global_nvs
padding at the end is also removed.

If device_nvs_t exists, place a properly sized reserve for
chromeos_acpi_t in the middle.

Allocation from cbmem is adjusted such that it matches exactly
the OperationRegion size defined inside the ASL.

Change-Id: If234075e11335ce958ce136dd3fe162f7e5afdf7
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/48788
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>

src/vendorcode/google/chromeos/gnvs.h

@@ -10,10 +10,7 @@
 
 /*
  * chromeos_acpi_t portion of ACPI GNVS is assumed to live at
- * 0x100 - 0x1000.  When defining global_nvs, use check_member
- * to ensure that it is properly aligned:
- *
- *   check_member(global_nvs, chromeos, GNVS_CHROMEOS_ACPI_OFFSET);
+ * 0x100 - 0x1000.
  */
 #define GNVS_CHROMEOS_ACPI_OFFSET 0x100