MAINTAINERS: correct rtc armada38x pattern entry

Commit c6a95dbe

 ("MAINTAINERS: add the RTC driver for the
Armada38x") typoed the pattern, fix it.

Signed-off-by: Joe Perches <joe@perches.com>
Acked-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>