cros_bundle_firmware: Move entry creation into a function
cros_bundle_firmware: Move entry creation into a function

Move the code into a function so we can call it in other places.

BUG=chromium-os:32468
TEST=manual
Verified as part of seaboard flashing.

Change-Id: I880b364f77c7b9a73d508b341390ce3ed611aee1
Reviewed-on: https://gerrit.chromium.org/gerrit/27163
Commit-Ready: Simon Glass <c00b0378376498bd9cd974c388df8854c0131d27@chromium.org>
Reviewed-by: Simon Glass <c00b0378376498bd9cd974c388df8854c0131d27@chromium.org>
Tested-by: Simon Glass <c00b0378376498bd9cd974c388df8854c0131d27@chromium.org>

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