fromupstream: Don't restrict patchwork ID to be number only.

Some patchwork site use Message ID for the patch_id (for example,
https://patchwork.kernel.org/project/linux-usb/list/), which is
currently unable to be picked by fromupstream.py.

Fix this by using a string instead of int for patch_id.

BUG=None
TEST=With usbpw pointed to
     https://patchwork.kernel.org/project/linux-usb/ in ~/.pwclientrc,
     test that `./fromupstream.py --bug None --test None
     pw://usbpw/1604403610-16577-2-git-send-email-jun.li@nxp.com` works

Change-Id: Ic94c718b0aa86f37a4b7009fc2ddb49a0f61d2c6
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/dev-util/+/2540107
Tested-by: Pi-Hsun Shih <pihsun@chromium.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Tzung-Bi Shih <tzungbi@chromium.org>
Commit-Queue: Pi-Hsun Shih <pihsun@chromium.org>
1 file changed