powerpc: mpc85xx: flush the l1 cache before cpu down in kexec

powerpc: mpc85xx: flush the l1 cache before cpu down in kexec

We observe a "Zero PT_NOTE entries found" warning when vmcore_init()
is running on the dump-capture kernel. Actually the PT_NOTE segments
is not empty, but the entries generated by crash_save_cpu() are not
flushed to the memory before we reset these cores. So we should flush
the l1 cache as what we do in cpu hotplug. With this change, we can
also kill the mpc85xx_smp_flush_dcache_kexec() since that becomes
unnecessary.

Please note: this only fix the issue on e500 core, we still need to
implement the function to flush the l2 cache for the e500mc core.
Fortunately we already had proposing patch for this support [1].
Hope we can fix this issue for e500mc after that merged.

[1] https://lists.ozlabs.org/pipermail/linuxppc-dev/2014-March/115830.html

Signed-off-by: Kevin Hao <haokexin@gmail.com>
Signed-off-by: Scott Wood <scottwood@freescale.com>