proc_fill_cache(): just make instantiate_t return int

all instances always return ERR_PTR(-E...) or NULL, anyway

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --cc fs/proc/base.c
Simple merge

diff --cc fs/proc/fd.c
Simple merge

diff --cc fs/proc/internal.h
Simple merge

diff --cc fs/proc/namespaces.c
Simple merge