servo_updater: account for versions starting with v2
servo_updater: account for versions starting with v2

With resent base tag update the hardcoded version number pattern
in servo_updater.py needs to be adjusted.

BRANCH=none
BUG=b:112475211
TEST=TBD

Change-Id: If3b18f563ff48eb98db95864d8f2298ead04495d
Signed-off-by: Vadim Bendebury <5515d6d2d0829cbe0dd0dcf2094aaded06d58514@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1237714
Reviewed-by: Nick Sanders <f4566bb3c90c0bf5fa0906b296b1da45051a62ee@chromium.org>

coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec