thermal: rcar_gen3_thermal: add delay in .thermal_init on r8a7796
The .thermal_init needs to be delayed a short amount of time to allow
for the TEMP register to contain something useful. If it's not delayed
these warnings are common during boot:
thermal thermal_zone0: failed to read out thermal zone (-5)
thermal thermal_zone1: failed to read out thermal zone (-5)
thermal thermal_zone2: failed to read out thermal zone (-5)
The warnings are triggered by the first call to .get_temp() while the
TEMP register contains 0 and rcar_gen3_thermal_get_temp() returns -EIO
since a TEMP value of 0 will result in a temperature reading which is
out of specifications.
This should have been done in the initial commit which adds the driver
as the same issue was found and corrected for r8a7795.