seccomp: make function __get_seccomp_filter static

The function __get_seccomp_filter is local to the source and does
not need to be in global scope, so make it static.

Cleans up sparse warning:
symbol '__get_seccomp_filter' was not declared. Should it be static?
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Fixes: 66a733ea ("seccomp: fix the usage of get/put_seccomp_filter() in seccomp_get_filter()")
Cc: stable@vger.kernel.org
Signed-off-by: NKees Cook <keescook@chromium.org>

kernel/seccomp.c

@@ -473,7 +473,7 @@ static long seccomp_attach_filter(unsigned int flags,
 	return 0;
 }
 
-void __get_seccomp_filter(struct seccomp_filter *filter)
+static void __get_seccomp_filter(struct seccomp_filter *filter)
 {
 	/* Reference count is bounded by the number of total processes. */
 	refcount_inc(&filter->usage);