i2c: Deprecate legacy RTC drivers

We have a new RTC subsystem with better drivers.

Legacy driver status:
* ds1337: The DS1337 and DS1339 are now supported by the rtc-ds1307
  driver, so it looks to me like we could even delete the ds1337
  driver right away.
* ds1374: Will soon be replaced with Scott Wood's rtc-ds1374 driver.
* m41t00: The M41T00 is supported by the rtc-ds1307 driver. For the
  M41T81 and M41T85, the rtc-m41t80 driver written by Atsushi Nemoto
  should work.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Acked-by: Mark A. Greer <mgreer@mvista.com>
Acked-by: James Chapman <jchapman@katalix.com>
Cc: Randy Vinson <rvinson@mvista.com>