staging: regulator: hi6421v600-regulator: initialize ramp_delay

Without that, the regulator's core complains with:

       ldo17: ramp_delay not set

For now, use the enable time, as we don't have any datasheets from
this device.
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/67df5456e4f23c88ab4fd9331eb8202c3952e5c5.1597647359.git.mchehab+huawei@kernel.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/hikey9xx/hi6421v600-regulator.c

@@ -267,6 +267,9 @@ static int hi6421_spmi_dt_parse(struct platform_device *pdev,
 		return ret;
 	}
 
+	/* FIXME: are there a better value for this? */
+	rdesc->ramp_delay = rdesc->enable_time;
+
 	/* parse .eco_uA */
 	ret = of_property_read_u32(np, "eco-microamp",
 				   &sreg->eco_uA);