OMAPDSS: APPLY: Remove unnecessary call to mg_clear_shadow_dirty

OMAPDSS: APPLY: Remove unnecessary call to mg_clear_shadow_dirty

When doing a manual update in dss_mgr_start_update, we clear the shadow dirty
flags. Although there isn't any harm in clearing them. The need to clear them
out here should never arrive.

When applying configurations for a manual update manager, we never do any
register writes, i.e, calls to dss_mgr_write_regs and dss_mgr_write_regs_extra
never happen while applying. We do all these writes only when we call
dss_mgr_start_update. Hence, there is never a time when the shadow registers
are dirty.

Remove the call to mg_clear_shadow_dirty.

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