OMAP: DSS2: FEATURES: DSI PLL parameter cleanup

The DSI PLL parameters (regm, regn, regm_dispc, regm_dsi, fint) have different
fields and also different Max values on OMAP3 and OMAP4. Use dss features to
calculate the register fields and min/max values based on current OMAP revision.

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