i2c-eg20t: Fix bus-idle waiting issue

Currently, when checking whether bus is idle or not,
if timeout occurs,
this function always returns success(zero).
This patch fixes the issue.

Signed-off-by: Tomoya MORINAGA <tomoya-linux@dsn.lapis-semi.com>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>