i2c-eg20t: Modify returned value s32 to long

Type of wait_event_timeout is long not s32.
This patch replaces s32 with long.
Additionally, delete negative processing(ret < 0).

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