pinctrl: imx21: Remove the MODULE_DEVICE_TABLE() macro

Commit e2756baa ("pinctrl: imx21: make it explicitly non-modular")
missed the removal of the MODULE_DEVICE_TABLE() macro causing the
following build error:

drivers/pinctrl/freescale/pinctrl-imx21.c:328:1: error: data definition has no type or storage class [-Werror]
 MODULE_DEVICE_TABLE(of, imx21_pinctrl_of_match);

,so remove the macro to fix this problem.

Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Fabio Estevam <festevam@gmail.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>