MAINTAINERS: Update linus' git repository

Change to new git tree -
 (git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git).

Signed-off-by: Tracey Dent <tdent48227@gmail.com>
Acked-by: WANG Cong <xiyou.wangcong@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>