findmissing: Make fixes table argument optional

The SHA is typically sufficient to identify a specific commit.
In most cases, having to specify the affected table (stable or chrome)
is just a nuisance. On top of that, the current implementation makes
it difficult to find entries where a single patch fixes problems
in different tables. Make the affected table an optional argument.

This change enables output such as:

$ ./findmissing status b6aa06de7757
Table   Branch  SHA             Fixed by SHA    Status
stable  5.4     1fa27418054f    b6aa06de7757    OPEN
chrome  4.14    3068f5d40e65    b6aa06de7757    ABANDONED
chrome  4.14    bad5e0c830c8    b6aa06de7757    OPEN

If a provided SHA exists more than once in any affected table,
the '-f' parameter is still needed to enforce an action.

BUG=None
TEST=Run various findmissing commands

Change-Id: I6c100c3548e02b8947746f4b653558233422a3d9
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/dev-util/+/2316712
Tested-by: Guenter Roeck <groeck@chromium.org>
Reviewed-by: Curtis Malainey <cujomalainey@chromium.org>
Commit-Queue: Guenter Roeck <groeck@chromium.org>
3 files changed