Input: remove useless synchronize_rcu() calls

There is no need to call synchronize_rcu() after a list insertion,
or a NULL->ptr assignment.

However, the reverse operations do need this call.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

diff --cc drivers/input/evdev.c
Simple merge

diff --cc drivers/input/input.c
Simple merge

diff --cc drivers/input/joydev.c
Simple merge

diff --cc drivers/input/mousedev.c
Simple merge