rtc: delete legacy MAINTAINERS entry

People stumble across the entry for the legacy PC specific RTC driver
entry in MAINTAINERS when they really want the multi-arch, multi-driver
RTC subsystem.  So just delete the old entry that is causing the
confusion.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>