ARM: STi: Remove platform call to trace_hardirqs_off()

Calling trace_hardirqs_off() from the platform specific
secondary startup code as not been necessary since Dec 2010
when Russell King consolidated the call into the common SMP
code.

2c0136db ARM: SMP: consolidate trace_hardirqs_off() into common SMP code

Signed-off-by: Peter Griffin <peter.griffin@linaro.org>
Signed-off-by: Maxime Coquelin <maxime.coquelin@st.com>