OMAPDSS: DISPC: program dispc polarities to control module

On DRA7xx, DISPC needs to write output signal polarities not only to a
DISPC register, like for all earlier DSS versions, but to control
module's CTRL_CORE_SMA_SW_1 register.

This patch adds support to write the polarities to control module.

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