it85spi: EOL support

This code was originally introduced by ITE for now exceedingly old
Chromebooks. The code has had very little attention to maintain it,
unlikely tested for a long time and now seems to be just a technical
burden to the flashrom project.

If someone is later interested it could be resurrected for reference
from git history. However, it needs quite a bit of work to bring it back
into maintainable order.

BUG=b:156143896,b:170689483
TEST=tree builds under meson+make and unit tests pass.

Change-Id: I5e8cafd73db837941c518f0e2d72d8192274fd79
Signed-off-by: Edward O'Callaghan <quasisec@google.com>
Reviewed-on: https://review.coreboot.org/c/flashrom/+/65378
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Reviewed-by: Anastasia Klimchuk <aklm@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

meson.build

@@ -271,7 +271,6 @@ if config_internal
       'amd_imc.c',
       'dmi.c',
       'ichspi.c',
-      'it85spi.c',
       'it87spi.c',
       'mcp6x_spi.c',
       'sb600spi.c',