Make kobj_methods constant.

These structures hold no information that is modified during runtime. By
marking this constant, we see approximately 600 symbols become
read-only (amd64 GENERIC). While there, also mark the kobj_method
structures generated by makeobjops.awk static. They are only referenced
by the kobjop_desc structures within the same file.

Before:

	$ ls -l kernel
	-rwxr-xr-x  1 ed  wheel  15937309 Nov  8 16:29 kernel*
	$ size kernel
	    text    data     bss      dec    hex filename
	12260854 1358468 2848832 16468154 fb48ba kernel
	$ nm kernel | fgrep -c ' r '
	8240

After:

	$ ls -l kernel
	-rwxr-xr-x  1 ed  wheel  15922469 Nov  8 16:25 kernel*
	$ size kernel
	    text    data     bss      dec    hex filename
	12302869 1302660 2848704 16454233 fb1259 kernel
	$ nm kernel | fgrep -c ' r '
	8838

1 files changed, 1 insertions, 1 deletions

diff --git a/sys/kern/subr_kobj.c b/sys/kern/subr_kobj.c
index 4ee7182..23ad29f 100644
--- a/sys/kern/subr_kobj.c
+++ b/sys/kern/subr_kobj.c
@@ -92,7 +92,7 @@ SYSINIT(kobj, SI_SUB_LOCK, SI_ORDER_ANY, kobj_init_mutex, NULL);
  * desc pointer is NULL, it is guaranteed never to match any read
  * descriptors.
  */
-static struct kobj_method null_method = {
+static const struct kobj_method null_method = {
 	0, 0,
 };