rtc: bd70528: Add MODULE ALIAS to autoload module

rtc: bd70528: Add MODULE ALIAS to autoload module

The bd70528 RTC driver is probed by MFD driver. Add MODULE_ALIAS
in order to allow udev to load the module when MFD sub-device cell
for RTC is added.

I'm not sure if this is a bugfix or feature addition but I guess
fixes tag won't harm in this case.

Fixes: 3c7ab69c7355 ("rtc: bd70528: Initial support for ROHM bd70528 RTC")
Signed-off-by: Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
Link: https://lore.kernel.org/r/20191023114711.GA13954@localhost.localdomain
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>