Add missing semi-colon to sb.s_bdi check

This fixes a regression introduced by
b83e3e48c9b183a80dd00eb6c7431a1cbc7d89c9 on Linux 3.0 and possibly other
kernels where sb.s_bdi was not being properly detected.

Reported-by: DHE
Signed-off-by: Richard Yao <ryao@gentoo.org>