tools: genboardscfg.py, use default terminal size if
 undetectable

The existing terminalsize detection raised an exception on build
server. Removes the exception and return 0 columns instead. This
also deactivates the progress indicator.

Signed-off-by: Roger Meier <roger@bufferoverflow.ch>
CC: Masahiro Yamada <yamada.m@jp.panasonic.com>
CC: Tom Rini <trini@ti.com>
---
Changes for v2:
   - use 24 instead of 25 lines
Changes for v3:
   - return integer with 0 columns instead of tuple
     this deactivates the progress indicator