xtensa: drop EXPORT_SYMBOL for outs*/ins*

Custom outs*/ins* implementations are long gone from the xtensa port,
remove matching EXPORT_SYMBOLs.
This fixes the following build warnings issued by modpost since commit
15bfc234 ("modpost: check for static EXPORT_SYMBOL* functions"):

  WARNING: "insb" [vmlinux] is a static EXPORT_SYMBOL
  WARNING: "insw" [vmlinux] is a static EXPORT_SYMBOL
  WARNING: "insl" [vmlinux] is a static EXPORT_SYMBOL
  WARNING: "outsb" [vmlinux] is a static EXPORT_SYMBOL
  WARNING: "outsw" [vmlinux] is a static EXPORT_SYMBOL
  WARNING: "outsl" [vmlinux] is a static EXPORT_SYMBOL

Cc: stable@vger.kernel.org
Fixes: d38efc1f ("xtensa: adopt generic io routines")
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

arch/xtensa/kernel/xtensa_ksyms.c

@@ -119,13 +119,6 @@ EXPORT_SYMBOL(__invalidate_icache_range);
 // FIXME EXPORT_SYMBOL(screen_info);
 #endif
 
-EXPORT_SYMBOL(outsb);
-EXPORT_SYMBOL(outsw);
-EXPORT_SYMBOL(outsl);
-EXPORT_SYMBOL(insb);
-EXPORT_SYMBOL(insw);
-EXPORT_SYMBOL(insl);
-
 extern long common_exception_return;
 EXPORT_SYMBOL(common_exception_return);