OMAPDSS: DSI: use common DSS PLL support

Now that we have the common DSS PLL support, change DSI to use it. This
results in quite a lot of changes, but almost all of them are trivial
name changes.

The functions to calculate and program the PLL settings can be removed
from dsi.c, as the common PLL API contains the same functionality.

We also need to create struct dss_pll_hw entries for PLL hardware
features for different OMAP platforms, instead of using the
dss_features.c as the old code does.

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