drivers: gpio: rz: Mass renaming

Mass renaming is carried out to unify some prefixes and shorten some
macros, making the code easier to maintain and support new devices.

- Rename `int_dev` to `gpio_int_dev` for gpio interrupt
- Rename `eirq` to `ext_irq` for external interrupt
- Rename `gpio_rz_hw_config` to `gpio_rz_flags`
- Rename `p_pm` to `gpio_flags`
- Rename `pre_flags` to `rz_flags`
- Remove `_IOPORT` and `_PIN_CONFIGURE` in some macros
- Rename `GPIO_RZ_PIN_CONFIGURE_GET_FILTER`,
  `GPIO_RZ_PIN_CONFIGURE_GET`, `GPIO_RZ_PIN_SPECIAL_FLAG_GET` to
  `GPIO_RZ_FLAG_GET_FILTER`, `GPIO_RZ_FLAG_GET_CONFIG`,
  `GPIO_RZ_FLAG_GET_SPECIFIC` respectively

Signed-off-by: Nhut Nguyen <nhut.nguyen.kc@renesas.com>