pflash: Bury disabled code to limit device sizes

We disabled code to limit device sizes to 8, 16, 32 or 64MiB more than
a decade ago in commit 95d1f3ed and c8b153d7, v0.9.1.  Bury.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
[Extracted from a larger patch, extended to pflash_cfi02.c]
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20190319163551.32499-3-armbru@redhat.com>