cros_bundle_firmware: Pollute EC RO binary FMAP signature
cros_bundle_firmware: Pollute EC RO binary FMAP signature

We don't want to have two FMAP signatures in the image. At present
the EC RO binary includes an FMAP signature since for write-enabled
devices we still use flashrom to perform the EC RO update.

This is a temporary situation since s/w sync will eventually do the
RO bin image - see example CL here:

https://gerrit.chromium.org/gerrit/#/c/30866/

For now, change the fmap signature on this blob to __fMAP__ for this
blob only.

BUG=chrome-os-partner:13143
BRANCH=snow,link
TEST=manual
Check flashrom's fmap.h and see the signature:

Run 'cros_bundle_firmware -b daisy -d exynos5250-snow -O out'

Use ghex to look at out/updated-ecro.bin and see that it does not
include __FMAP__ anymore (the 'F' is changed to 'f').

Same with image:

$ strings out/image.bin |grep -i __fmap__
__fMAP__
__FMAP__

(the last one is the real FMAP)

Change-Id: I58789684184123bb2f914cbf2a28fc0199c5ddb2
Reviewed-on: https://gerrit.chromium.org/gerrit/31612
Reviewed-by: Randall Spangler <62698fdbb84d1779579ee80c3f39fac22017e5bc@chromium.org>
Commit-Ready: Simon Glass <c00b0378376498bd9cd974c388df8854c0131d27@chromium.org>
Tested-by: Simon Glass <c00b0378376498bd9cd974c388df8854c0131d27@chromium.org>

mgireesh05/dev-util,coreos/dev-util,marineam/coreos-dev-util,coreos/dev-util,coreos/dev-util,mgireesh05/dev-util,marineam/coreos-dev-util,mgireesh05/dev-util