ARM: dts: Drop duplicate sha2md5_fck to fix clk_disable race

We have a duplicate legacy clock defined for sha2md5_fck that can
sometimes race with clk_disable() with the dts configured clock
for OMAP4_SHA2MD5_CLKCTRL when unused clocks are disabled during
boot causing an "Unhandled fault: imprecise external abort".

Signed-off-by: Tony Lindgren <tony@atomide.com>