nios2: ksyms: Add missing symbol exports

Building nios2:allmodconfig fails as follows (each symbol is only listed
once).

ERROR: "__ashldi3" [drivers/md/dm-writecache.ko] undefined!
ERROR: "__ashrdi3" [fs/xfs/xfs.ko] undefined!
ERROR: "__ucmpdi2" [drivers/media/i2c/adv7842.ko] undefined!
ERROR: "__lshrdi3" [drivers/md/dm-zoned.ko] undefined!
ERROR: "flush_icache_range" [drivers/misc/lkdtm/lkdtm.ko] undefined!
ERROR: "empty_zero_page" [drivers/md/dm-mod.ko] undefined!

The problem is seen with gcc 7.3.0.

Export the missing symbols.

Fixes: 2fc8483f ("nios2: Build infrastructure")
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Ley Foon Tan <ley.foon.tan@intel.com>

arch/nios2/kernel/nios2_ksyms.c

@@ -9,12 +9,20 @@
 #include <linux/export.h>
 #include <linux/string.h>
 
+#include <asm/cacheflush.h>
+#include <asm/pgtable.h>
+
 /* string functions */
 
 EXPORT_SYMBOL(memcpy);
 EXPORT_SYMBOL(memset);
 EXPORT_SYMBOL(memmove);
 
+/* memory management */
+
+EXPORT_SYMBOL(empty_zero_page);
+EXPORT_SYMBOL(flush_icache_range);
+
 /*
  * libgcc functions - functions that are used internally by the
  * compiler...  (prototypes are not correct though, but that
@@ -31,3 +39,7 @@ DECLARE_EXPORT(__udivsi3);
 DECLARE_EXPORT(__umoddi3);
 DECLARE_EXPORT(__umodsi3);
 DECLARE_EXPORT(__muldi3);
+DECLARE_EXPORT(__ucmpdi2);
+DECLARE_EXPORT(__lshrdi3);
+DECLARE_EXPORT(__ashldi3);
+DECLARE_EXPORT(__ashrdi3);