OMAP2420: clock: add sdrc_ick

Add sdrc_ick to the OMAP2420 clock data so the clock code can control
the CM_AUTOIDLE bit associated with this clock.

Signed-off-by: Paul Walmsley <paul@pwsan.com>
Tested-by: Rajendra Nayak <rnayak@ti.com>
Reviewed-by: Kevin Hilman <khilman@ti.com>