procfs: kill ->proc_dops

procfs: kill ->proc_dops

It has two possible values - one for "forced lookup" entries, another
for the normal ones.  We'd be better off with that as an explicit
flag anyway and in addition to that it opens some fun possibilities
with ->d_op and ->d_flags handling.

[moved PROC_ENTRY_FORCE_LOOKUP to include/linux/proc_fs.h, switched it
to an unused bit - there was a conflict]

Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>