drivers/rtc/rtc-twl.c: fix rtc_reg_map initialization

Initialize the rtc_reg_map in platform_driver's probe function instead at
module_init time.  This way we can make sure that the twl-core has been
already probed and initialized (twl_priv->twl_id is valid) since the
platform device for the RTC driver will be created by the twl-core after
it finished its init.

Reported-by: Christoph Fritz <chf.fritz@googlemail.com>
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Tested-by: Kevin Hilman <khilman@linaro.org>
Tested-by: Grygorii Strashko <grygorii.strashko@ti.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>