emacs: remove popwin

Signed-off-by: Yoshifumi Hosoya <yoshifumi.hosoya.wj@renesas.com>
emacs: remove spell check

Signed-off-by: Yoshifumi Hosoya <yoshifumi.hosoya.wj@renesas.com>
emacs: remove yasnipet

Signed-off-by: Yoshifumi Hosoya <yoshifumi.hosoya.wj@renesas.com>
emacs: add function mode

Signed-off-by: Yoshifumi Hosoya <yoshifumi.hosoya.wj@renesas.com>