Input: do not corrupt system-wide procfs fops.

entry->proc_fops is a pointer to struct file_operations. When we
call create_proc_entry(...), it pointis to proc_file_operations,
deep in fs/proc/generic.c. By adding a 'poll' member to this struct
we effectively force the 'poll' member on every file in /proc,
which is wrong (they all fail select(...) calls).

This patch changes a copy of entry->proc_fops and reassigns it rather
than changing the original member.

Signed-off-by: Dmitry Torokhov <dtor@mail.ru>