m32r: fix build failure

m32r allmodconfig build was failing with the error:

  ERROR: "smp_flush_cache_all" [drivers/misc/lkdtm.ko] undefined!

lkdtm driver at drivers/misc is using flush_icache_range() which for
m32r is defined as smp_flush_cache_all() if CONFIG_SMP is defined.  But
as smp_flush_cache_all() was not exported so the build was failing with
the error of undefined symbol.

Link: http://lkml.kernel.org/r/1464001182-8329-1-git-send-email-sudipm.mukherjee@gmail.com
Signed-off-by: Sudip Mukherjee <sudip.mukherjee@codethink.co.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/m32r/kernel/smp.c

@@ -164,6 +164,7 @@ void smp_flush_cache_all(void)
 	spin_unlock(&flushcache_lock);
 	preempt_enable();
 }
+EXPORT_SYMBOL(smp_flush_cache_all);
 
 void smp_flush_cache_all_interrupt(void)
 {