mfd: da9063: Replace mfd_add_devices with devm counterpart

Use devm_mfd_add_devices() instead of plain mfd_add_devices(), which
removes the need for da9063_device_exit() altogether and also for the
.remove callback in da9063-i2c.c .

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>