reset: convert of_reset_control_get_count() to using firmware nodes

reset: convert of_reset_control_get_count() to using firmware nodes

Start the conversion of reset core to using firmware nodes by reworking
of_reset_control_get_count(). Unfortunately there is no fwnode-based
alternative to of_count_phandle_with_args() so we have to hand-code it.

Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>