arch: unicore32: ksyms: export '__cpuc_coherent_kern_range' to avoid compiling failure

flush_icache_range() is '__cpuc_coherent_kern_range' under unicore32,
and lkdtm.ko needs it. At present, '__cpuc_coherent_kern_range' is
still used by unicore32, so export it to avoid compiling failure.

The related error (with allmodconfig under unicore32):

  ERROR: "__cpuc_coherent_kern_range" [drivers/misc/lkdtm.ko] undefined!
Signed-off-by: Chen Gang <gang.chen.5i5j@gmail.com>
Acked-by: Xuetao Guan <gxt@mprc.pku.edu.cn>
Signed-off-by: Xuetao Guan <gxt@mprc.pku.edu.cn>

arch/unicore32/mm/proc-syms.c

@@ -19,5 +19,7 @@
 EXPORT_SYMBOL(cpu_dcache_clean_area);
 EXPORT_SYMBOL(cpu_set_pte);
 
+EXPORT_SYMBOL(__cpuc_coherent_kern_range);
+
 EXPORT_SYMBOL(__cpuc_dma_flush_range);
 EXPORT_SYMBOL(__cpuc_dma_clean_range);