bitmap: fix seq_bitmap and seq_cpumask to take const pointer

Impact: cleanup

seq_bitmap just calls bitmap_scnprintf on the bits: that arg can be const.
Similarly, seq_cpumask just calls seq_bitmap.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
diff --git a/fs/seq_file.c b/fs/seq_file.c
index 16c2115..c99358a 100644
--- a/fs/seq_file.c
+++ b/fs/seq_file.c
@@ -462,7 +462,8 @@
 	return -1;
 }
 
-int seq_bitmap(struct seq_file *m, unsigned long *bits, unsigned int nr_bits)
+int seq_bitmap(struct seq_file *m, const unsigned long *bits,
+				   unsigned int nr_bits)
 {
 	if (m->count < m->size) {
 		int len = bitmap_scnprintf(m->buf + m->count,