OMAP: DSS2: Remove omap_dss_device argument from dsi_pll_init()

The function dsi_pll_init() has omap_dss_device argument which is
not used. Remove this argument.

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