ARM: msm: fix section mismatch warning

WARNING: vmlinux.o(.text+0x9037c): Section mismatch in reference from
the function bring_up_cpu() to the function .cpuinit.text:cpu_up()
The function bring_up_cpu() references
the function __cpuinit cpu_up().
This is often because bring_up_cpu lacks a __cpuinit
annotation or the annotation of cpu_up is wrong.

Fix the above warning by adding __cpuinit annotation.

Signed-off-by: Igor Grinberg <grinberg@compulab.co.il>