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/[e-mail]
Signed-off-by: Sudip Mukherjee <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

arch/m32r/kernel/smp.c

···
 	spin_unlock(&flushcache_lock);
 	preempt_enable();
 }
+EXPORT_SYMBOL(smp_flush_cache_all);
 
 void smp_flush_cache_all_interrupt(void)
 {