powerpc/fsl-booke: Move loadcam_entry back to asm code to fix SMP ftrace

powerpc/fsl-booke: Move loadcam_entry back to asm code to fix SMP ftrace

commit 78f622377f7d31d988db350a43c5689dd5f31876 upstream.

When we build with ftrace enabled its possible that loadcam_entry would
have used the stack pointer (even though the code doesn't need it).  We
call loadcam_entry in __secondary_start before the stack is setup.  To
ensure that loadcam_entry doesn't use the stack pointer the easiest
solution is to just have it in asm code.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>