build: don't place mnttab.o in source directory

Breaks cross-arch build.

Signed-off-by: Avi Kivity <avi@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
net: Kill unused struct protosw inetsw[]

It is #if 0'd.

Spotted during code inspection.

Signed-off-by: Asias He <asias@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>