locking/refcounts: Do not force refcount_t usage as GPL-only export

The refcount_t protection on x86 was not intended to use the stricter
GPL export. This adjusts the linkage again to avoid a regression in
the availability of the refcount API.
Reported-by: Dave Airlie <airlied@gmail.com>
Fixes: 7a46ec0e ("locking/refcounts, x86/asm: Implement fast refcount overflow protection")
Cc: stable@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/x86/mm/extable.c

@@ -82,7 +82,7 @@ bool ex_handler_refcount(const struct exception_table_entry *fixup,
 
 	return true;
 }
-EXPORT_SYMBOL_GPL(ex_handler_refcount);
+EXPORT_SYMBOL(ex_handler_refcount);
 
 /*
  * Handler for when we fail to restore a task's FPU state.  We should never get