OMAP: DSS2: Remove CONFIG_OMAP2_DSS_SLEEP_BEFORE_RESET

CONFIG_OMAP2_DSS_SLEEP_BEFORE_RESET is used to avoid an unclear bug at
DSS reset time. The pm runtime will handle reset in the future, and this
code has to be removed. Hopefully we won't see this error anymore.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>