vfs: room for 32 disks and partitions, 32 mounts, 16 SchFS volumes

NBLKDEV was 16 for every disk and partition together, which a laptop's
NVMe drive with its eight partitions and a USB stick come close to. The
mount table held 8, SchFS 4 volumes and 4 snapshots, FAT 4 volumes.
Now 32, 32, 16, 8 and 8; the device numbers still fit between the ones
already fixed.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01S1giNvrHTrPMPw7V6x1kQ4

kernel/dev/procfs.c

@@ -245,7 +245,7 @@ gen_mounts(struct sbuf *sb)
 
   // Every mount is in the table, /dev included. A fixed devtmpfs line here
   // listed it twice once init mounted it the ordinary way.
-  for (int i = 0; i < 16; i++) {
+  for (int i = 0; i < 32; i++) {
     if (mount_get(i, path, source, type, &fsdev) != 0)
       continue;
     // "/" is emitted last, below, so skip it if it somehow appears here.

kernel/fs/fs.c

@@ -1584,7 +1584,7 @@ skipelem(char *path, char *name, int *toolong)
 // a subtree becomes a place you can walk into and never out of.
 // ===========================================================================
 
-#define NMOUNT 8
+#define NMOUNT 32
 
 static struct {
   struct spinlock lock;