correct name for rtc-m41t80

The new rtc-m41t80 driver name doesn't match its module name, which
prevents it from properly hotplugging.  Since it's new, no platforms yet
depend on that name ...  so this patch fixes the driver name to match its
module name, rather than going the other way around with a MODULE_ALIAS().

NOTE: This sort of bug is a new thing to watch out for with new-style I2C
drivers; previously I2C couldn't hotplug.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Acked-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>