drivers: interrupt controller: Add support for RZ/T

- Add interrupt controller driver support for RZ/T
- Remove a duplicate USE_RZ_FSP_EXT_IRQ in Kconfig

Signed-off-by: Quang Le <quang.le.eb@bp.renesas.com>
Signed-off-by: Nhut Nguyen <nhut.nguyen.kc@renesas.com>
Signed-off-by: Binh Nguyen <binh.nguyen.xw@renesas.com>