openEuler: add openEuler/MAINTAINERS for Maintainers & Committers

openEuler inclusion
category: doc
bugzilla: https://gitee.com/openeuler/kernel/issues/I63OX8



Add the Maintainer & Committers list for the openEuler/kernel repository
by referring to the MAINTAINERS file of the upstream community.
It is convenient to obtain the list of Maintainers & Committers of the
openEuler/kernel based on the submitted PR or patches.

Only the of the scheduling subsystem is added to openEuler/MAINTAINERS.
This is used as a reference for other modules and subsystems.

Example:
$./scripts/get_maintainer.pl -no-l --no-rolestats
--maintainer-path=openEuler/MAINTAINERS --no-tree --no-fixes
--no-git-blame-signatures --no-git-fallback
0001-sched-fair-Fix-fault-in-reweight_entity.patch

Signed-off-by: Xie XiuQi <xiexiuqi@huawei.com>