Revert "pinctrl: digicolor: add missing platform_set_drvdata() call"

This reverts commit 8b2b3dcb.

Commit 546c6d79 (pinctrl: digicolor: make it explicitly non-modular) removed
the platform_get_drvdata() call, so platform_set_drvdata() is no longer needed.

Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>