riscv: fix compile failure with EXPORT_SYMBOL() & !MMU

When support for !MMU was added, the declaration of
__asm_copy_to_user() & __asm_copy_from_user() were #ifdefed
out hence their EXPORT_SYMBOL() give an error message like:
  .../riscv_ksyms.c:13:15: error: '__asm_copy_to_user' undeclared here
  .../riscv_ksyms.c:14:15: error: '__asm_copy_from_user' undeclared here

Since these symbols are not defined with !MMU it's wrong to export them.
Same for __clear_user() (even though this one is also declared in
include/asm-generic/uaccess.h and thus doesn't give an error message).

Fix this by doing the EXPORT_SYMBOL() directly where these symbols
are defined: inside lib/uaccess.S itself.

Fixes: 6bd33e1e ("riscv: fix compile failure with EXPORT_SYMBOL() & !MMU")
Reported-by: kbuild test robot <lkp@intel.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>

arch/riscv/kernel/riscv_ksyms.c

@@ -9,8 +9,5 @@
 /*
  * Assembly functions that may be used (directly or indirectly) by modules
  */
-EXPORT_SYMBOL(__clear_user);
-EXPORT_SYMBOL(__asm_copy_to_user);
-EXPORT_SYMBOL(__asm_copy_from_user);
 EXPORT_SYMBOL(memset);
 EXPORT_SYMBOL(memcpy);

arch/riscv/lib/uaccess.S

 #include <linux/linkage.h>
+#include <asm-generic/export.h>
 #include <asm/asm.h>
 #include <asm/csr.h>
 
@@ -66,6 +67,8 @@ ENTRY(__asm_copy_from_user)
 	j 3b
 ENDPROC(__asm_copy_to_user)
 ENDPROC(__asm_copy_from_user)
+EXPORT_SYMBOL(__asm_copy_to_user)
+EXPORT_SYMBOL(__asm_copy_from_user)
 
 
 ENTRY(__clear_user)
@@ -108,6 +111,7 @@ ENTRY(__clear_user)
 	bltu a0, a3, 5b
 	j 3b
 ENDPROC(__clear_user)
+EXPORT_SYMBOL(__clear_user)
 
 	.section .fixup,"ax"
 	.balign 4