thermal: max77620: Appease the kernel-doc deity

Fix up the following warning when compiled with make W=1:

linux.git/drivers/thermal/max77620_thermal.c:48: warning: Function
parameter or member 'temp' not described in 'max77620_thermal_read_temp'

Signed-off-by: Amit Kucheria <amit.kucheria@linaro.org>
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/c943d51e7913a4b73cda447547b8ee77c857f7ba.1574242756.git.amit.kucheria@linaro.org