drivers: i2c: nrfx_twim: simplify PM by using pm_device_driver_init

- Driver always initializes the device in the suspended state
- If CONFIG_PM_DEVICE_RUNTIME=n, device PM callback will be called with
  RESUME action, thus setting up pins to default state and enabling the
  peripheral

NOTE: when CONFIG_PM_DEVICE=n, the pinctrl sleep state will not be
available (-ENOENT) and so never applied, thus avoiding a pin
suspended->active transition.

Signed-off-by: Gerard Marull-Paretas <gerard@teslabs.com>