iio: adc: rzg2l_adc: Enable runtime PM autosuspend support

iio: adc: rzg2l_adc: Enable runtime PM autosuspend support

Enable runtime PM autosuspend support for the rzg2l_adc driver. With this
change, consecutive conversion requests will no longer cause the device to
be runtime-enabled/disabled after each request. Instead, the device will
transition based on the delay configured by the user.

This approach reduces the frequency of hardware register access during
runtime PM suspend/resume cycles, thereby saving CPU cycles.

Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Reviewed-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Link: https://patch.msgid.link/20241206111337.726244-9-claudiu.beznea.uj@bp.renesas.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>