cros_bundle_firmware: Add support for bus specifiers
cros_bundle_firmware: Add support for bus specifiers

When flashing to SPI, the SPI flash chip can be on buses other than bus
0. Provide a parameter so that the caller can select this.

BUG=chromium-os:19724
TEST=manual: run cros_bundle_firmware -w on Seaboard
See that it still flashes correctly.

Change-Id: Ie5ab318cabc7df1bc8ebe888009242a5bfafa6fc
Reviewed-on: https://gerrit.chromium.org/gerrit/18324
Commit-Ready: Simon Glass <c00b0378376498bd9cd974c388df8854c0131d27@chromium.org>
Reviewed-by: Simon Glass <c00b0378376498bd9cd974c388df8854c0131d27@chromium.org>
Tested-by: Simon Glass <c00b0378376498bd9cd974c388df8854c0131d27@chromium.org>

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