pinctrl: coh901: fix initconst annotation

Clang correctly points out that the section attribute for u300_gpio_confdata
is in the wrong place:

drivers/pinctrl/pinctrl-coh901.c:130:37: error: '__section__' attribute only applies to functions and global variables

This moves it from the type name to the variable, so it actually gets
discarded.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>