gpio: ts5500: Delete platform data handling

The TS5500 GPIO driver apparently supports platform data
without making any use of it whatsoever. Delete this code,
last chance to speak up if you think it is needed.

Cc: kernel@savoirfairelinux.com
Cc: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Cc: Jerome Oufella <jerome.oufella@savoirfairelinux.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>