MAINTAINERS: update maintainership of LTP

The maintainership of LTP is out of date, so update it.

Signed-off-by: Wanlong Gao <gaowanlong@cn.fujitsu.com>
Signed-off-by: Cyril Hrubis <chrubis@suse.cz>
Signed-off-by: Caspar Zhang <caspar@casparzhang.com>
Reviewed-by: Rishikesh K Rajak <rishikesh.rajak@hp.com>
Acked-by: Subrata Modak <tosubrata@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>