ARM: OMAP2+: dmtimer: cleanup iclk usage

We do not use iclk anywhere in the dmtimer driver and so removing it.
Hence removing the timer iclk entries from OMAP4 clkdev table as well.

Signed-off-by: Tarun Kanti DebBarma <tarun.kanti@ti.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>