OMAP: DSS2: DSI: Remove DISPC pixel clock related info in dsi_dump_clocks()

dsi_dump_clocks() prints lck and pck rates for the DISPC channel which it is
connected to. Remove this since it is already printed by dispc_dump_clocks()
in debugfs.

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