ARM: dts: omap54xx-clocks: Correct abe_iclk clock node

abe_iclk's parent is aess_fclk and not abe_clk.
Also correct the parameters for clock rate calculation as used for OMAP4
since in PRCM level there's no difference between the two platform
regarding to AESS/ABE clocking.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Acked-by: Tero Kristo <t-kristo@ti.com>
Signed-off-by: Tero Kristo <t-kristo@ti.com>