ARM: OMAP2PLUS: DSS: Disable LCD3 output when resetting DSS

The dispc_disable_outputs() function currently disables all LCD managers except
LCD3. This patch adds disabling functionality for LCD3 manager thereby
maintaining consistency of Display Subsystem for in case Display Controller is
reset when LCD3 manager is in use.

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