ARM: OMAP3: use CLK_SET_RATE_PARENT for dss clocks

Set CLK_SET_RATE_PARENT flag for dss1_alwon_fck_3430es2,
dss1_alwon_fck_3430es1 and dpll4_m4x2_ck so that the DSS's fclk can be
configured without the need to get the parent's parent of the fclk.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>