OMAPDSS: DISPC: pass pclk & lclk to dispc_ovl_calc_scaling

In order to make the scaling calculations independent of the current
hardware configuration (e.g. which manager is connected to this output),
we need to change the calc funcs to get all the variables needed for the
calculations via parameters.

This patch changes dispc_ovl_calc_scaling to get pclk and lclk as
parameters.

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