[ARM] OMAP24xx clock: add missing SSI L4 interface clock

This patch adds a missing OMAP24xx clock, the SSI L4 interface clock,
as "ssi_l4_ick".

linux-omap source commit is ace129d39b3107d330d4cf6934385d13521f2fec.

Signed-off-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>