drm/sti: use new Reset API

Since 0b52297f

 ("reset: Add support for shared reset controls") the
new Reset API now demands consumers choose either an *_exclusive or a
*_shared line when requesting reset lines.

This issue was found when running a kernel containing the aforementioned
patch  which includes an informitive WARN().  It implies that one or
more used reset lines are in fact shared.  This is why we're using the
*_shared variant.

Signed-off-by: Lee Jones <lee.jones@linaro.org>
Acked-by: Peter Griffin <peter.griffin@linaro.org>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: http://patchwork.freedesktop.org/patch/msgid/20160725100933.9261-1-lee.jones@linaro.org