cros_bundle_firmware: Correct BL1 and BL2 default names

Now that the names have changed, the defaults should be updated also.

Leave the model code there since it may be needed depending on what
we decide to do about the various BL1 options.

BUG=chrome-os-partner:18447
BUG=chromium:249379
TEST=manual
Run crosfw script and see that it no longer gives errors about missing
BL1 file.

Change-Id: I303e7f1ff32b7364dc0692603cb9c46fec091842
Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/58628
1 file changed