security/vboot: Deprecate VBOOT_VBNV_EC

Boards using VBOOT_VBNV_EC (nyan, daisy, veyron, peach_pit) are all
ChromeOS devices and they've reached the end of life since Feb 2022.
Therefore, remove VBOOT_VBNV_EC for them, each with different
replacement.

- nyan (nyan, nyan_big, nyan_blaze): Add RW_NVRAM to their FMAP (by
  reducing the size of RW_VPD), and replace VBOOT_VBNV_EC with
  VBOOT_VBNV_FLASH.
- veyron: Add RW_NVRAM to their FMAP (by reducing the size of
  SHARED_DATA), and replace VBOOT_VBNV_EC with VBOOT_VBNV_FLASH. Also
  enlarge the OVERLAP_VERSTAGE_ROMSTAGE section for rk3288 (by reducing
  the size of PRERAM_CBMEM_CONSOLE), so that verstage won't exceed its
  allotted size.
- daisy: Because BOOT_DEVICE_SPI_FLASH is not set, which is required for
  VBOOT_VBNV_FLASH, disable MAINBOARD_HAS_CHROMEOS and VBOOT configs.
- peach_pit: As VBOOT is not set, simply remove the unused VBOOT_VBNV_EC
  option.

Remove the VBOOT_VBNV_EC Kconfig option as well as related code, leaving
VBOOT_VBNV_FLASH and VBOOT_VBNV_CMOS as the only two backend options for
vboot nvdata (VBNV).

Also add a check in read_vbnv() and save_vbnv() for VBNV options.

BUG=b:178689388
TEST=util/abuild/abuild -t GOOGLE_NYAN -x -a
TEST=util/abuild/abuild -t GOOGLE_VEYRON_JAQ -x -a
TEST=util/abuild/abuild -t GOOGLE_DAISY -a
TEST=util/abuild/abuild -t GOOGLE_PEACH_PIT -a
BRANCH=none

Change-Id: Ic67d69e694cff3176dbee12d4c6311bc85295863
Signed-off-by: Yu-Ping Wu <yupingso@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/65012
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>

Documentation/security/vboot/index.md

@@ -176,7 +176,6 @@ CMOS, the EC, or in a read/write area of the SPI flash device.
 Select one of the following:
 
 * `VBOOT_VBNV_CMOS`
-* `VBOOT_VBNV_EC`
 * `VBOOT_VBNV_FLASH`
 
 More non-volatile storage features may be found in `security/vboot/Kconfig`.