Input: wistron_btns - fix incorrect placement of __initconst

__initconst should be placed between the variable name and equal
sign for the variable to be placed in the intended section.

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>