tests: drivers: counter_seconds: Convert to use DEVICE_DT_GET

Move to use DEVICE_DT_GET instead of device_get_binding as
we work on phasing out use of DTS 'label' property.

Note: the CONFIG_COUNTER_CMOS driver is devicetree based so we can
remove the hardcoded "CMOS" and use DT_COMPAT_GET_ANY_STATUS_OKAY.

Signed-off-by: Kumar Gala <galak@kernel.org>