floss_patches: Add `fix_upstream` command `fix_upstream` rebases the upstream patches to ToT. The developer would be asked to resolve the conflicts in the .../Bluetooth/upstream repo on the local storage, and re-run `fix_upstream` with the `--continue` flag. Then the script would help update the patch files in the overlay. BUG=b:315096774 TEST=floss_patches fix_upstream; floss_patches fix_upstream --continue Change-Id: Ic98dcb0577eff26e2b9c1c9471a98bba622eda17 Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/bluetooth/+/5179897 Commit-Queue: Hsin-chen Chuang <[email protected]> Reviewed-by: Dean Liao <[email protected]> Tested-by: Hsin-chen Chuang <[email protected]>