MAINTAINERS: erofs: complete sub-entries for erofs

Add a formal git tree and missing files for erofs
after moving out of staging for everyone to blame
in order for better improvement.
Acked-by: Chao Yu <yuchao0@huawei.com>
Link: https://lore.kernel.org/r/20190919062838.106423-1-gaoxiang25@huawei.comSigned-off-by: Gao Xiang <gaoxiang25@huawei.com>

MAINTAINERS

@@ -6112,7 +6112,10 @@ M:	Gao Xiang <gaoxiang25@huawei.com>
 M:	Chao Yu <yuchao0@huawei.com>
 L:	linux-erofs@lists.ozlabs.org
 S:	Maintained
+T:	git git://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs.git
+F:	Documentation/filesystems/erofs.txt
 F:	fs/erofs/
+F:	include/trace/events/erofs.h
 
 ERRSEQ ERROR TRACKING INFRASTRUCTURE
 M:	Jeff Layton <jlayton@kernel.org>