msm: headsmp.S: Fix section mismatch

WARNING: vmlinux.o(.cpuinit.text+0xc80): Section mismatch in
reference from the function boot_secondary() to the variable
.init.text:msm_secondary_startup
The function __cpuinit boot_secondary() references a variable
__init msm_secondary_startup.  If msm_secondary_startup is only
used by boot_secondary then annotate msm_secondary_startup with
a matching annotation.

Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: David Brown <davidb@codeaurora.org>